Antes de la presentación, tengo miedo de quedarme en blanco.

Because when antes is followed by a noun or an infinitive, Spanish normally uses de.

• antes de la presentación = before the presentation
• antes de hablar = before speaking

You can use antes alone when no noun or infinitive follows:

• Llegué antes. = I arrived earlier.

Because presentación is a feminine noun: la presentación.

In Spanish, de + el contracts to del, but de + la does not contract.

• de el libro → del libro
• de la presentación stays de la presentación

Both are possible, but tener miedo is very common in everyday Spanish.

• Tengo miedo de quedarme en blanco = very natural, conversational
• Temo quedarme en blanco = also correct, but often sounds a bit more formal or literary

So the sentence uses the more common spoken pattern.

Because Spanish normally says tener miedo de + noun / infinitive when you say what someone is afraid of.

• Tengo miedo de los perros.
• Tengo miedo de fallar.
• Tengo miedo de quedarme en blanco.

So de is part of the usual structure.

Because the verb here is quedarse, not just quedar.

Quedarse en blanco is a fixed expression meaning to go blank. In this sentence, the subject is yo, so the reflexive pronoun is me:

• quedarme = for me to go blank

If the subject changed, the pronoun would change too:

• quedarte = for you to go blank
• quedarse = for him/her/you formal to go blank
• quedarnos = for us to go blank

Because Spanish attaches object/reflexive pronouns to an infinitive.

So after de, you get:

• de quedarme
• de sentarme
• de olvidarlo

If the verb were conjugated, the pronoun would usually go before it:

• Me quedo en blanco.
• Me siento.

So quedarme is the normal infinitive form with the pronoun attached.

Yes, it is an idiomatic expression.

Literally, en blanco means blank or in blank/white, but quedarse en blanco means:

• to go blank
• to freeze mentally
• to suddenly forget what you were going to say

It is especially common when talking about exams, speeches, interviews, or presentations.

Because the feeling exists now.

The sentence means that right now, before the presentation, I am afraid of what might happen. Spanish, like English, often uses the present tense for a current emotion about a future event.

So:

• Tengo miedo... = I am afraid...
• the fear is present
• the possible mental blank happens later

It is acceptable, but not absolutely necessary.

Antes de la presentación is an introductory phrase. In Spanish, a comma after an introductory phrase can be used to mark a pause:

• Antes de la presentación, tengo miedo de quedarme en blanco.

Without the comma, the sentence is still correct:

• Antes de la presentación tengo miedo de quedarme en blanco.

The version with the comma feels slightly more paused or carefully written.

Yes, both are possible, but they are slightly different in focus.

• Antes de la presentación = before the presentation event
• Antes de presentar = before presenting
• Antes de hacer la presentación = before giving/making the presentation

The original sentence focuses on the time before the event itself, which is very natural.

Yes. In this context, presentación is the normal word for a presentation, especially a talk, oral presentation, or formal presentation in class or at work.

Depending on context, Spanish can also use more specific words, but presentación is the standard and most general choice here.

No. It is common in speaking situations, but it can also be used for memory or thinking in general.

For example:

• during an exam
• during an interview
• while answering a question
• while trying to remember something

It always suggests that your mind suddenly stops producing the information you need.