memai ga hidoi node, sibaraku isu ni suwatte yasumimasu.

In めまいがひどい, が marks めまい as the thing that has the condition ひどい.

So the structure is basically:

• めまい = dizziness
• が = subject marker
• ひどい = severe / bad

This is a very natural way in Japanese to describe symptoms or conditions:

• 頭が痛い = my head hurts / I have a headache
• 気分が悪い = I feel sick
• めまいがひどい = the dizziness is severe

You could use は in some contexts for contrast or topic-marking, but が is the neutral, natural choice here.

Here, ひどい means severe, bad, or terrible.

With symptoms, it often means the symptom is strong or serious:

• 咳がひどい = the cough is bad
• 頭痛がひどい = the headache is severe
• めまいがひどい = the dizziness is severe

So it does not mean the dizziness is morally “awful”; it means it is intense or serious.

ので means because, and it sounds a bit more explanatory, softer, and often more polite than から.

In this sentence:

• めまいがひどいので、しばらく椅子に座って休みます。
• Because my dizziness is severe, I’ll sit in a chair and rest for a while.

If you used から instead:

• めまいがひどいから、しばらく椅子に座って休みます。

that would also be correct, but から can sound a little more direct or conversational.

A rough nuance:

• ので = giving a reason in a calm, explanatory way
• から = giving a reason more directly

Japanese often leaves out subjects and possessives when they are obvious from context.

So めまいがひどいので naturally implies:

• I am badly dizzy
• my dizziness is severe

Likewise, 休みます implies that I will rest, because the speaker is talking about their own action.

This kind of omission is extremely common in Japanese.

しばらく means for a while, for a little while, or for some time.

It gives an approximate duration, not an exact one.

So:

• しばらく休みます = I’ll rest for a while
• しばらく待ってください = please wait a moment / for a little while

In this sentence, it means the speaker plans to sit and rest temporarily, not permanently or for a long, fixed period.

The verb 座る usually takes に to mark the place where someone sits.

So:

• 椅子に座る = sit on a chair
• 床に座る = sit on the floor

With 座る, に is the normal particle.

Using で would not sound natural here, because で usually marks:

• the place where an action happens
• the means/tool used to do something

But 座る specifically tends to pair with に for the place/target of sitting.

The て-form connects actions.

Here:

• 座って = sit down / sit
• 休みます = rest

Together, 座って休みます means:

• sit down and rest
• sit and rest
• rest while sitting

The て-form often links actions in sequence or related actions:

• 家に帰って寝ます = I’ll go home and sleep
• 水を飲んで休みます = I’ll drink some water and rest

So in this sentence, the speaker first sits down, then rests.

It can suggest both, and that is normal in Japanese.

The basic idea is:

1. sit down
2. rest

But because the actions are closely connected, it also naturally implies:

• I’ll rest while sitting in a chair

Japanese often leaves that relationship flexible when the meaning is obvious from context.

休みます is the polite present/future form of 休む.

It is used because the sentence is in polite style:

• ひどいので
• 休みます

This kind of style is common in:

• speaking to strangers
• workplace situations
• medical situations
• generally polite conversation

The plain version would be:

• めまいがひどいので、しばらく椅子に座って休む。

That sounds less polite and more casual.

めまい is the noun dizziness or vertigo.

Japanese often expresses symptoms as [symptom] が + adjective rather than using have.

So instead of saying something literally like I have severe dizziness, Japanese says:

• めまいがひどい
• literally, the dizziness is severe

This is a very common Japanese pattern for physical conditions.

Yes, 椅子 is the normal kanji spelling, and it is already written that way here.

Some other words are in hiragana because that is standard or very common:

• めまい: often written in hiragana in everyday writing, even though there are kanji forms such as 目眩
• が, ので, に, て: particles and endings are normally in hiragana
• しばらく: usually written in hiragana
• ひどい: usually written in hiragana, though 酷い exists

So the mixture of kanji and hiragana here is completely natural Japanese spelling.

The comma is not absolutely required, but it is very natural and helpful.

It separates:

• the reason: めまいがひどいので
• the main action: しばらく椅子に座って休みます

So it makes the sentence easier to read:

• Because my dizziness is severe, I’ll sit in a chair and rest for a while.

Japanese commas are often used more flexibly than English commas, but here the comma clearly marks the pause after the reason clause.

Yes. That is a very natural English translation.

The Japanese order is:

• reason first: めまいがひどいので
• action second: しばらく椅子に座って休みます

But in English, you can translate it naturally in either order:

• Because my dizziness is severe, I’ll sit in a chair and rest for a while.
• I’m very dizzy, so I’m going to sit down and rest for a while.

Both capture the meaning well.