jump out of (one's) skin

Translations
подпрыгнуть от испуга
I nearly jumped out of my skin when the fire alarm went off.
Я чуть не подпрыгнул от испуга, когда сработала пожарная сигнализация.
Definitions
To be extremely startled, frightened, or surprised, often to the point of having a strong physical reaction.