A veces, únicamente necesito sentarme en silencio y respirar hondo.

A veces means sometimes. It is a very common fixed expression in Spanish.

• a = at / on / sometimes part of set phrases
• veces = times

So literally it is something like at times, which matches sometimes in English.

You could also hear algunas veces, but a veces is shorter and more common in everyday speech.

Yes, here únicamente means only or just.

In this sentence:

• únicamente necesito... = I only need...

It is very similar to:

• solo necesito...
• solamente necesito...

The differences are mainly about style:

• solo = very common, natural
• solamente = also common, slightly fuller
• únicamente = a bit more formal or emphatic

All three work here.

Spanish often leaves out subject pronouns because the verb ending already shows who the subject is.

• necesito = I need
• the -o ending tells you it is yo

So yo necesito is possible, but it is usually unnecessary unless you want emphasis or contrast:

• Yo necesito descansar, pero él quiere salir.
  I need to rest, but he wants to go out.

In your sentence, necesito by itself is the most natural choice.

Because sentarse is a reflexive verb, and when a reflexive verb is used in the infinitive, the reflexive pronoun can attach to the end.

• sentar = to seat, to sit someone down
• sentarse = to sit down

So:

• sentarme = to sit myself down / more naturally, to sit down

After a conjugated verb like necesito, Spanish commonly uses:

• necesito sentarme
• quiero acostarme
• voy a ducharme

This is completely normal.

Not sentar-me with a hyphen. In standard Spanish, it is written as one word: sentarme.

You can also place the reflexive pronoun before the conjugated verb in some structures, but not here with exactly the same meaning. The natural options are:

• Necesito sentarme.
• Me necesito sentar. → this sounds odd and unnatural in most contexts

With necesitar + infinitive, the normal form is:

• Necesito sentarme.

So for this sentence, sentarme is the correct and idiomatic choice.

Because the meaning is to sit down, and in Spanish that is usually the reflexive verb sentarse.

Compare:

• sentar = to seat someone / to place someone in a sitting position
• sentarse = to sit down

Examples:

• Voy a sentar al niño. = I’m going to seat the child.
• Voy a sentarme. = I’m going to sit down.

So in your sentence, the speaker is talking about themselves sitting down, which is why sentarme is used.

Because en silencio is the most natural and idiomatic way to say in silence or quietly in this context.

• sentarme en silencio = sit down in silence / sit quietly

Spanish often prefers a noun phrase like en silencio where English might use an adverb.

Silenciosamente exists, but it is less common in everyday speech and can sound more literary or formal. In this sentence, en silencio sounds much more natural.

Respirar hondo means to breathe deeply or to take a deep breath.

Literally:

• respirar = to breathe
• hondo = deep

This is a very common Spanish expression. Even though English usually says breathe deeply, Spanish often says respirar hondo rather than respirar profundamente.

Both can be understood, but respirar hondo is the more idiomatic everyday phrasing.

Because with respirar, Spanish normally uses the fixed expression respirar hondo.

Even though profundo also means deep, it is not the usual word in this expression. So learners should treat respirar hondo as a set phrase.

A few useful patterns:

• respirar hondo = breathe deeply
• dar un respiro hondo is less standard than dar un respiro profundo in some contexts, but respirar hondo is the common verb phrase

So the important thing is: with respirar, hondo is what native speakers typically say.

The comma after A veces is possible because it is an introductory expression at the beginning of the sentence.

• A veces únicamente necesito...
• A veces, únicamente necesito...

Both are acceptable. The comma creates a small pause and can make the sentence easier to read. In short sentences like this, the comma is often a stylistic choice rather than a strict necessity.

Yes, adverbs like únicamente can often move around, though the emphasis may change slightly.

Your sentence has:

• A veces, únicamente necesito sentarme en silencio y respirar hondo.

This emphasizes that the only thing the speaker needs is that simple action.

Other possible placements:

• A veces, necesito únicamente sentarme en silencio y respirar hondo.
• A veces, solo necesito sentarme en silencio y respirar hondo.

These are all understandable. The original sentence sounds natural, and placing únicamente before necesito gives a clear all I need is... feeling.

Yes. Here y connects two infinitives:

• sentarme en silencio
• respirar hondo

Both depend on necesito:

• necesito sentarme...
• necesito respirar...

So the full idea is:

• Sometimes, I only need to sit quietly and breathe deeply.

Spanish often avoids repeating the verb when one verb governs two infinitives.

The original sentence is perfectly correct and natural, but in more casual everyday speech, many speakers might say:

• A veces solo necesito sentarme en silencio y respirar hondo.

This version uses solo instead of únicamente, which sounds a bit more conversational.

So:

• únicamente = correct, a bit more careful or formal
• solo = very common and everyday

Both are good Spanish.