Sebelum tidur, saya mengecek alarm ponsel sekali lagi.

In Indonesian, the subject is often left out in a time phrase if it is already obvious from the main clause.

So:

• sebelum tidur = before sleeping / before going to sleep
• sebelum saya tidur = before I sleep / before I go to sleep

Both are possible, but sebelum tidur sounds more natural and compact here because the main clause already has saya, so the listener easily understands that the sleeper is the same person.

Here, tidur is functioning verbally: to sleep / sleeping.

Indonesian does not mark verbs the way English does with forms like sleep, to sleep, and sleeping. A basic verb form like tidur can cover several of these meanings depending on context.

After sebelum, tidur naturally means sleeping or going to sleep.

Mengecek is the active verb form built from cek.

The prefix meN- often marks an active verb in Indonesian. With some short or borrowed bases, it appears as menge-, so:

• cek = check
• mengecek = to check

Using mengecek sounds more like a complete standard verb in a sentence. In casual speech, people do also say cek by itself, as in saya cek dulu.

Yes. It comes from English check, but it has been adapted into Indonesian spelling and grammar.

That is very common in Indonesian: a borrowed word can still take Indonesian affixes. So even though the root came from English, mengecek behaves like an Indonesian verb.

A more formal or more fully native-style alternative would be memeriksa.

Indonesian usually puts the main noun first and the describing noun after it.

So:

• alarm ponsel = phone alarm
• literally: alarm of a phone

The thing being talked about is alarm, and ponsel tells you what kind of alarm it is.

This noun order is very normal in Indonesian. English often does the reverse, which is why it can feel unusual to learners.

Ponsel means cell phone / mobile phone.

Related words:

• ponsel = standard Indonesian word for a mobile phone
• telepon = phone in general
• HP = very common informal way to say handphone / mobile phone

So alarm ponsel specifically means the alarm on a mobile phone.

Sekali lagi is a very common expression meaning one more time or once again.

Parts:

• sekali = once
• lagi = again / more

Together, they emphasize a single extra repetition: one more time.

If you say just lagi, the meaning again is still possible, but sekali lagi sounds fuller and more natural here because the idea is checking the alarm one last extra time before sleep.

That position is natural because it modifies the action mengecek.

So the sentence flows like this:

• Sebelum tidur = time
• saya mengecek alarm ponsel = main action
• sekali lagi = how many extra times the action happens

Putting sekali lagi at the end sounds very natural in Indonesian. It is similar to English saying I check my phone alarm one more time.

The comma separates the introductory time phrase from the main clause.

• Sebelum tidur, = Before sleeping,
• saya mengecek alarm ponsel sekali lagi. = main statement

This is standard punctuation and helps readability. In very informal writing, people may leave the comma out, but using it here is correct.

Yes.

• saya = neutral, polite, standard
• aku = more casual and personal

So:

• Sebelum tidur, saya mengecek alarm ponsel sekali lagi.
  sounds neutral and standard.
• Sebelum tidur, aku mengecek alarm ponsel sekali lagi.
  sounds more casual and conversational.

The grammar stays the same; only the tone changes.