Learn Hardcore Russian: Иногда я становлюсь нервным перед экзаменом. - Sometimes I become nervous before an exam.

Иногда я становлюсь нервным… = Sometimes I become / I get nervous…
If you used быть (which is usually just omitted in the present), it would describe a static state:
- Я нервный перед экзаменом. = I am (by nature / generally) a nervous person before an exam.

So становлюсь focuses on the transition from “not nervous” to “nervous,” which matches the English “get nervous.”

What does the reflexive ending -сь in становлюсь do here?

The -сь (or -ся after a consonant) is the reflexive ending. It marks становиться as a reflexive / intransitive verb.

Infinitive: становиться (to become)
1st person singular: я становлюсь

Historically it is “to make oneself become,” but for a learner it’s easiest just to remember that “to become” in Russian is reflexive by default and is always used with -ся / -сь in its personal forms. You cannot say я становлю with this meaning.

Why is it нервным and not нервный?

Нервным is in the instrumental case, masculine singular.

With verbs meaning “to be” and “to become” (for roles, professions, states, characteristics), Russian normally puts the complement in the instrumental:

Я был студентом. – I was a student.
Он стал врачом. – He became a doctor.
Я становлюсь нервным. – I become nervous.

So:

нервный – nominative (dictionary form, used for “a nervous man/person,” etc.)
нервным – instrumental, used here as “become nervous” as a state.

The instrumental after становиться / стать is the standard pattern for this kind of “become X” structure.

Could I say Иногда я нервничаю перед экзаменом instead? What’s the difference?

Yes, Иногда я нервничаю перед экзаменом is completely natural and very common.

Nuance:

становлюсь нервным – emphasizes the change of state: at some point you become nervous.
нервничаю (from нервничать) – describes the ongoing experience or behavior of being nervous.

In most everyday contexts they are close in meaning, and both sound fine.
If you want to highlight the moment when your calmness changes into nervousness, становлюсь нервным is more precise.

Why is it перед экзаменом and why is экзаменом in the instrumental case?

The preposition перед (“before; in front of”) always takes the instrumental case in Russian.

Space: перед домом – in front of the house
Time: перед экзаменом – before the exam

So the noun экзамен must be in the instrumental: экзаменом.
You cannot say перед экзамен; with перед the instrumental is obligatory.

Why is it singular экзаменом and not plural экзаменами, if I mean “before exams” in general?

Russian very often uses the singular to talk about a typical / repeated situation in general:

Я опаздываю на работу. – I’m late for work (in general, not one specific day).
Я боюсь темноты. – I’m afraid of the dark.

Similarly:

Иногда я становлюсь нервным перед экзаменом.
= Sometimes I get nervous before an exam / before exams (whenever I have an exam).

You can say перед экзаменами, but that sounds a bit more like “before the exams” as a set (for example, a whole exam session). The singular is the most natural neutral choice for “before an exam (whenever I have one).”

Can I move иногда or other words around? For example, is Я иногда становлюсь нервным перед экзаменом okay?

Yes, Russian word order is quite flexible, and several variants are correct:

Иногда я становлюсь нервным перед экзаменом.
Я иногда становлюсь нервным перед экзаменом.

Both are natural. Small nuances:

Starting with Иногда makes the frequency (“sometimes”) the first thing you hear – stylistically a bit closer to English.
Я иногда становлюсь… puts a bit more initial focus on the subject я (“I sometimes become…”).

Versions like Я становлюсь нервным иногда перед экзаменом are possible but sound less neutral and more marked in rhythm/focus; for learners, it’s safest to keep иногда near the beginning or right after я.

What’s the difference between становиться and стать here? Could I say Иногда я стану нервным перед экзаменом?

Становиться (impf.) and стать (pf.) form an aspect pair:

становиться – imperfective, focuses on process / repeated action
стать – perfective, focuses on single completed change / result

In the present:

я становлюсь нервным – present, repeated / general: I (sometimes) become nervous.
я стану нервным is future: I will become nervous.

Because иногда usually describes a repeated, typical situation, Иногда я стану нервным перед экзаменом sounds odd; it suggests repeated references to future single events, not a general fact about you.

For habitual meaning with иногда, you want the imperfective: Иногда я становлюсь нервным…

Could I say до экзамена instead of перед экзаменом? Is there a difference?

You can say both, but they’re not identical:

перед экзаменом – literally “right before the exam,” often implying the time immediately leading up to it (e.g., the previous evening, the moments before it starts).
до экзамена – “before the exam,” more general; it can mean any time earlier than the exam, not necessarily immediately before.

So:

Я волнуюсь перед экзаменом. – I’m nervous as the exam approaches / right before it.
Я волнуюсь задолго до экзамена. – I worry long before the exam.

In your sentence, перед экзаменом is perfect because it matches the idea of feeling nervous as the exam approaches.

How would the sentence change if the speaker is a woman?

Only the adjective needs to agree in gender with the subject:

Male speaker: Иногда я становлюсь нервным перед экзаменом.
Female speaker: Иногда я становлюсь нервной перед экзаменом.

Нервной is the feminine singular instrumental form of the adjective, matching я when the speaker is female. The verb становлюсь stays the same for both genders.