Empecé a tartamudear al principio de la presentación porque me sentía muy torpe.

This is one of the most important things to notice in the sentence.

• Empecé = preterite because it describes a completed action or a specific moment: I started.
• Me sentía = imperfect because it describes an ongoing internal state or background feeling: I was feeling / I felt.

So the sentence combines:

• a main event: Empecé a tartamudear
• with a background cause or emotional state: porque me sentía muy torpe

A native-English way to think about it is:

• I started stuttering = a definite event
• because I felt awkward = the feeling was already there in the background

If you said me sentí, it would sound more like a specific moment when that feeling came over you, rather than an ongoing emotional state during the situation.

Because the verb is empezar, but in the yo form of the preterite the spelling changes:

• empezar → empecé

This happens because Spanish changes z to c before e to keep the same sound.

Compare:

• empezar → empecé
• cruzar → crucé
• almorzar → almorcé

So empecé is not irregular in meaning, but it does have a spelling change for pronunciation.

It means to start/begin to do something.

So:

• Empecé a tartamudear = I started to stutter

This structure is very common in Spanish:

• Empezó a llover = It started to rain
• Voy a empezar a estudiar = I’m going to start studying
• Empezaron a hablar = They started talking

After empezar a, you use the infinitive of the next verb.

Because after empecé a, Spanish uses the infinitive.

So:

• Empecé a tartamudear = correct
• Empecé a tartamudeé = incorrect

This is the same pattern as in English:

• I started to stutter
• not I started I stuttered

The infinitive here is tartamudear = to stutter / to stammer.

Tartamudear means to stutter or to stammer.

It can refer to:

• an actual speech disorder
• or temporary stumbling over words because of nerves, fear, embarrassment, etc.

In this sentence, it most likely means the speaker began speaking in a broken, hesitant way because they felt uncomfortable.

Related words:

• tartamudo / tartamuda = a person who stutters
• hablar tartamudeando = to speak while stuttering

Al principio de means at the beginning of.

So:

• al principio de la presentación = at the beginning of the presentation

It is made from:

• a + el = al
• principio = beginning
• de la presentación = of the presentation

Very common examples:

• al principio del libro = at the beginning of the book
• al principio de la clase = at the beginning of the class

Because al principio is the normal, natural way to say at the beginning in Spanish.

• al principio = at first / at the beginning
• en el principio is much less common in everyday Spanish and often sounds literary, historical, or biblical depending on context

So in normal conversation:

• Al principio de la reunión estaba nervioso. = natural
• En el principio de la reunión... = unusual

A useful contrast:

• al principio = at first / initially
• en principio = in principle / theoretically

Those two are easy to confuse.

Presentación often means presentation, especially a talk, speech, or formal introduction in front of an audience.

In this sentence, la presentación most naturally means:

• a school presentation
• a work presentation
• a formal talk

Depending on context, presentación can also mean:

• the act of introducing something
• appearance/presentation
• a product format in some contexts

But here, because of al principio and tartamudear, it clearly points to speaking in front of others.

In Spain, people might also say:

• exposición
• charla
• ponencia
  depending on the setting and level of formality.

Because the verb is sentirse, which means to feel in the emotional or subjective sense.

So:

• me sentía = I felt / I was feeling

The full verb is:

• sentirse = to feel

Examples:

• Me siento bien. = I feel well.
• Se sentía nervioso. = He was feeling nervous.
• Nos sentimos cansados. = We feel tired.

This me is the reflexive pronoun that matches yo.

Both can sometimes relate to feelings, but they are not used in exactly the same way.

• Me sentía torpe = I felt awkward/clumsy
• Estaba torpe = I was awkward/clumsy

The version with sentirse focuses more on the speaker’s personal perception or emotional experience.

So in this sentence:

• porque me sentía muy torpe = because that is how I felt inside

If you said porque estaba muy torpe, it would sound more like you are describing your actual state or behaviour from the outside.

Both can work in some contexts, but me sentía is more natural here because it explains the speaker’s inner feeling.

Torpe can mean several related things, depending on context:

• clumsy
• awkward
• inept
• bad at doing something
• sometimes even slow or dull in certain contexts

In this sentence, the best meaning is probably:

• awkward
• clumsy
• socially or mentally awkward in the moment

So me sentía muy torpe does not necessarily mean the speaker was physically clumsy. It more likely means:

• they felt awkward
• they felt they were handling the presentation badly
• they felt self-conscious and incapable

Not exactly.

• torpe = awkward, clumsy, inept
• avergonzado/a = embarrassed
• incómodo/a = uncomfortable

A person who feels torpe may also feel embarrassed, but the words are not the same.

In this sentence, torpe suggests:

• I felt awkward / clumsy / like I was messing things up

If you wanted to say I felt embarrassed, Spanish would more likely use:

• me sentía avergonzado
• or me daba vergüenza

Because porque means because, while por qué means why.

In this sentence, the speaker is giving a reason:

• porque me sentía muy torpe = because I felt very awkward

Compare:

• ¿Por qué tartamudeaste? = Why did you stutter?
• Tartamudeé porque estaba nervioso. = I stuttered because I was nervous.

A quick guide:

• porque = because
• por qué = why
• el porqué = the reason
• por que = rarer combination, different structure

The word order is natural, but Spanish is more flexible than English.

Original:

• Empecé a tartamudear al principio de la presentación porque me sentía muy torpe.

You could also say:

• Porque me sentía muy torpe, empecé a tartamudear al principio de la presentación.

That version gives slightly more emphasis to the reason.

You could even move other parts around depending on what you want to highlight, but the original order is the most neutral and natural.

The sentence is already natural. But depending on tone and context, a speaker from Spain might also say things like:

• Empecé a tartamudear al principio de la presentación porque estaba muy nervioso.
• Al principio de la presentación empecé a tartamudear porque me sentía muy incómodo.
• Empecé a trabarme al principio de la presentación porque me sentía muy torpe.

A small note:

• tartamudear is standard and clear
• trabarse can sometimes be used more colloquially for getting tongue-tied, though usage varies

So the original sentence is perfectly good standard Spanish.

A rough pronunciation guide:

• tartamudear ≈ tar-ta-moo-deh-AR
• sentía ≈ sen-TEE-a

A few useful points:

• In empecé, the stress is on the last syllable: em-pe-CÉ
• In sentía, the written accent shows that the stress falls on -tí-
• In Spain, c before e in empecé is pronounced with the th sound of Castilian Spanish: roughly em-pe-THÉ
• In most of Latin America, it sounds like s: em-pe-SÉ

Yes. Comenzar and empezar both mean to begin / to start.

So these are both correct:

• Empecé a tartamudear
• Comencé a tartamudear

In many everyday situations, empezar sounds a bit more common and conversational, but both are standard.

Their preterite forms:

• empecé
• comencé

So if you want a close synonym, comencé works very well.