get the jitters
To experience a temporary state of nervous anxiety or anticipation. A: "Are you ready to deliver your speech?" B: "Yeah. I've got a bad case of the jitters, though!"
get/have the ˈjitters
(informal) feel anxious and nervous, especially before an important event or before having to do something difficult: I always get the jitters before exams.Louise had the pre-wedding jitters so badly she nearly didn’t make it to the church.