Learn Hardcore Malay: Selepas makan tengah hari yang berat, saya sering berasa mengantuk di pejabat. - After a heavy lunch, I often feel sleepy at the office.

At the beginning (as in your sentence):
Selepas makan tengah hari yang berat, saya sering berasa mengantuk di pejabat.
It can come in the middle, but sounds a bit heavier/more written:
Saya sering berasa mengantuk di pejabat selepas makan tengah hari yang berat.

Both are grammatical. Starting with selepas is very natural when you want to emphasize the time/condition.

What is the difference between selepas, lepas, setelah, and sesudah?

All roughly mean after, but they differ in formality and frequency:

selepas – Standard, neutral, very common in both speech and writing.
lepas – Informal/colloquial version of selepas. Common in everyday conversation:
Lepas makan tengah hari yang berat, saya sering mengantuk di pejabat.
setelah – More formal/literary. Common in writing, speeches, stories:
Setelah makan tengah hari yang berat, saya sering berasa mengantuk di pejabat.
sesudah – Also formal, used less often in Malaysia; more common in Indonesian.

For everyday Malaysian Malay, selepas or lepas are the safest choices.

Why is it makan tengah hari and not just tengah hari if it already means “noon”?

tengah hari by itself means noon / midday (time of day).
makan tengah hari literally means midday eating, i.e. lunch.

So:

Selepas tengah hari = After noon (after 12 p.m. or so)
Selepas makan tengah hari = After lunch

Your sentence is specifically about feeling sleepy after lunch, not just after noon in general, so makan tengah hari is needed.

Is makan tengah hari always written as three words? I’ve seen makan tengahari or makan tengahari.

In standard Malay:

makan tengah hari = the officially correct spelling (three words).
tengah hari (two words) is the standard form for midday.

Common but less standard variants you may see:

makan tengahari / makan tengah-hari / makan tengahari – non-standard spellings, often found in casual writing, menus, social media, etc.

For exams, formal writing, or learning materials, stick to makan tengah hari.

What exactly does yang berat do here, and why does berat come after makan tengah hari?

yang is a relativizer/marker that links a noun to a description (similar to that / which / who in English, but used more broadly).

Structure:

makan tengah hari = lunch
yang berat = that is heavy / which is heavy
makan tengah hari yang berat = lunch that is heavy → a heavy lunch

In Malay, adjectives usually come after the noun:

makan tengah hari yang berat (lit. lunch that is heavy)
makanan yang pedas = spicy food
baju yang mahal = expensive clothes

So berat must come after and be linked by yang in this kind of noun phrase.

Could I just say Selepas makan tengah hari, saya sering berasa mengantuk di pejabat and drop yang berat?

Yes, you can. That becomes:

Selepas makan tengah hari, saya sering berasa mengantuk di pejabat.
= After lunch, I often feel sleepy in the office.

Dropping yang berat:

Makes the sentence more general.
Removes the nuance that it is specifically a heavy lunch that triggers sleepiness.

Both are grammatical; it just depends whether the “heaviness” of the lunch is important information.

Is berasa necessary here, or can I say saya sering mengantuk di pejabat?

Both are correct, but there is a nuance:

Saya sering berasa mengantuk di pejabat.
- berasa = to feel
- Literally: I often feel sleepy in the office.
- Slightly more formal/explicit, emphasizes the feeling.
Saya sering mengantuk di pejabat.
- mengantuk already works like to be sleepy / to feel sleepy.
- More direct and very natural in speech.

You could also say:

Selepas makan tengah hari yang berat, saya sering mengantuk di pejabat.

In everyday conversation, many people would drop berasa and just say mengantuk.

What is the difference between sering and selalu?

Both relate to frequency, but usage and nuance differ slightly:

sering = often / frequently
- Fairly neutral but can sound a bit more formal or written.
- Good in essays, reports, and also acceptable in speech.
selalu = always / usually / often, depending on context
- Extremely common in speech.
- Sometimes used where English would say often, not literally always.

Your sentence with selalu:

Selepas makan tengah hari yang berat, saya selalu berasa mengantuk di pejabat.
→ Very natural, sounds like “I often/always feel sleepy after a heavy lunch at the office.”

Both are fine; sering may be closer to English often in careful writing.

Why is sering placed before berasa? Can I move it?

In your sentence:

saya (subject)
sering (adverb: often)
berasa mengantuk (verb phrase: feel sleepy)

Standard, natural order is:

Subject + adverb of frequency + verb
→ Saya sering berasa mengantuk.

You can move sering in some ways, but they sound less natural or change focus:

Saya berasa sering mengantuk di pejabat.
Grammatically possible, but sounds slightly awkward; focus shifts more onto mengantuk being frequent rather than the whole feeling.
Sering, saya berasa mengantuk di pejabat.
Possible in writing to emphasize sering, but sounds stylistic/marked.

For everyday Malay, keep sering before the verb:
Saya sering berasa mengantuk di pejabat.

Why do we use di in di pejabat, and not pada or something else?

di is the basic preposition for in / at / on (location).

di pejabat = at the office / in the office (location)
di rumah = at home
di sekolah = at school

pada is used more for:

Time references: pada hari Isnin (on Monday)
Abstract/indirect objects: pada saya (to me / in my opinion)

So:

Saya di pejabat. = I am at the office.
Pada pejabat is generally wrong in this sense.

If you want to emphasize inside the office (not just at the building), you can also say:

di dalam pejabat = inside the office
but di pejabat is already natural and sufficient here.

Could I omit saya and just say Selepas makan tengah hari yang berat, sering berasa mengantuk di pejabat?

In this sentence, omitting saya is not natural.

Malay does often omit subject pronouns when the subject is obvious from context, but here:

Selepas makan tengah hari yang berat, sering berasa mengantuk di pejabat.
Without saya, it sounds incomplete, like “After a heavy lunch, often feel sleepy in the office” – who feels sleepy?

Better options:

Keep saya:
Selepas makan tengah hari yang berat, saya sering berasa mengantuk di pejabat.
Or, if context has already clearly established saya, then in a continuing conversation you might drop it in follow‑up sentences, but not usually in a sentence like this standing alone.

How would this sentence sound in very casual spoken Malay?

A natural informal version (especially in Malaysia) might be:

Lepas lunch berat, saya selalu mengantuk kat office.

Changes:

Selepas → Lepas (informal)
makan tengah hari → lunch (English borrowing, very common in speech)
yang berat → berat (you can drop yang in casual talk)
sering → selalu (more colloquial)
berasa mengantuk → mengantuk (shorter)
di pejabat → kat office (kat = informal di, office from English)

For learning, it’s useful to know both:

Formal/standard: Selepas makan tengah hari yang berat, saya sering berasa mengantuk di pejabat.
Colloquial: Lepas lunch berat, saya selalu mengantuk kat office.

What is the time difference between tengah hari and petang, and does it affect this sentence?

Malay time-of-day words:

pagi = morning
tengah hari = around noon, midday (roughly 12 p.m. – 1 p.m.)
petang = afternoon/early evening (roughly after lunch until sunset)

Your sentence uses makan tengah hari (lunch), which naturally happens around tengah hari. That’s why petang doesn’t appear.

If you wanted to say “In the afternoon I often feel sleepy at the office”, you could say:

Pada waktu petang, saya sering berasa mengantuk di pejabat.

But your original sentence specifically ties the sleepiness to after a heavy lunch, so tengah hari is the appropriate time word there.