Jump out of your skin
Definition 1 of 1
Pro Tip 1/3Intensity
The phrase often implies an extreme reaction, more than just being surprised. 
I jumped out of my skin when the alarm went off unexpectedly.
Pro Tip 2/3Colloquial Use
It's informal and best used in casual conversation or creative writing. 
She almost jumped out of her skin when her friend popped out of the box.
Pro Tip 3/3Figurative
The phrase is not literal; nobody actually jumps out of their skin. 
You made me jump out of my skin creeping up like that!