Unnerve (verb)

1. To make someone feel nervous, anxious or uncomfortable.
2. To cause to lose composure or confidence.

Origin:

Un + nerve.

Examples:

1. The sudden noise unnerved her.
2. The unexpected turn of events unnerved him.
3. He was unnerved by the silence of the crowd.
4. The thought of public speaking unnerved her.
5. The intense pressure unnerved the athlete and he made a mistake.