English idioms relating to
ANXIETY - FEAR - NERVOUSNESS

Afraid of one's own shadow

A person who is afraid of their own shadow is very nervous
  or easily frightened.
  "I've never seen anyone so easily scared - she's afraid of her
  own shadow."

Bundle of nerves

If you describe somebody as a bundle of nerves, you mean that
  they are very nervous, tense or worried.
  "My son is doing his driving test today. Needless to say he's a bundle
  of nerves!"

Have butterflies in your stomach

 If you have butterflies in your stomach, you are feeling very nervous.
  "At the beginning of an exam, I always have butterflies in my stomach."

Like a cat on hot bricks

A person who is like a cat on hot bricks is very nervous or restless.
  "The week before the results were published, she was like a cat on
  hot bricks."

On the edge of one's seat

 Someone who is on the edge of their seat is very interested in
  something and finds it both extremely exciting and nerve-wracking.
  "Look at Bob! He's on the edge of his seat watching that rugby match."