Quando tenho comichão no braço, tento não me coçar, mas às vezes começo a resmungar.

In European Portuguese, ter comichão is the normal way to express this idea. Literally, it is to have itch/itchiness.

This is similar to other common Portuguese expressions such as:

• ter fome = to be hungry
• ter sede = to be thirsty
• ter sono = to be sleepy

So even though English often uses to be + adjective, Portuguese often uses ter + noun for physical sensations.

Also, comichão usually appears without an article here. So tenho comichão is natural, while tenho uma comichão would sound more like I have an itch in a more specific, countable sense.

A useful note: in Portugal, comichão is very common. In Brazil, coceira is often more common.

Because this sentence describes a general or habitual situation: whenever I get itchy on the arm, I try not to scratch.

With quando, Portuguese can use different tenses depending on meaning:

• quando tenho comichão... = when/whenever I have an itch...
  This describes something that happens regularly or generally.
• quando tiver comichão... = when I get an itch...
  This points more to a specific future occasion.

So in this sentence, the present tense works because the speaker is talking about a repeated pattern, not one future event.

No is a contraction of em + o.

So:

• em o braço → no braço

This is completely standard in Portuguese. Similar contractions include:

• na = em + a
• nos = em + os
• nas = em + as

So no braço simply means in/on the arm, depending on the context.

Because Portuguese often leaves out the possessive with body parts when it is already obvious whose body part is meant.

So:

• tenho comichão no braço = natural
• tenho comichão no meu braço = possible, but more emphatic or contrastive

Since the subject is I, it is already clear that the arm is the speaker’s arm. English uses my more often here, but Portuguese usually does not need it.

Me is a reflexive pronoun. It shows that the action is being done to oneself.

So:

• coçar = to scratch
• coçar-me / me coçar = to scratch myself

In this sentence, tento não me coçar means I try not to scratch myself.

English often leaves myself out and just says I try not to scratch, but Portuguese commonly makes the reflexive idea explicit.

Because não normally attracts the clitic pronoun in Portuguese.

So after negation, the natural order is:

• não me coçar

not:

• não coçar-me

This is a very important pattern in European Portuguese. In many affirmative sentences, pronouns often come after the verb, but words like não trigger pronouns to come before it.

So here, tento não me coçar is the natural structure.

Yes, you could. It would still be correct.

There is a small difference in feel:

• tento não me coçar = I try not to scratch myself
• tento não coçar o braço = I try not to scratch my arm

The reflexive version is more general and very natural when talking about scratching your own body. The version with o braço is more specific because it names the body part directly.

Because começar is normally followed by a + infinitive in Portuguese.

So:

• começar a resmungar = to start grumbling
• começar a falar = to start speaking
• começar a rir = to start laughing

This is a standard verb pattern. English says start grumbling, but Portuguese needs the preposition a here.

Resmungar means something like:

• to grumble
• to mutter
• to complain under one’s breath

It usually suggests low-level complaining, irritation, or annoyed murmuring, rather than a full, direct complaint.

So in this sentence, the idea is not necessarily that the speaker starts making a formal complaint. It is more like they start grumbling because the itch is annoying.

Às vezes means sometimes.

The accent in às is a grave accent, and it marks the contraction of:

• a + as = às

This expression is fixed, so you should learn it as a chunk:

• às vezes = sometimes

Also, vezes is plural because the expression literally comes from the idea of at the times/occasions.

Yes, it sounds natural in European Portuguese.

A few things that make it especially natural for Portugal are:

• comichão is a very normal word in Portugal
• não me coçar has natural clitic placement
• começo a resmungar is standard and idiomatic

So this is a good sentence to learn from if your target is Portuguese from Portugal.