Ivy, has he been constantly nervous since? Or just sometimes?
How long was he in the crate for? Are you aware of everything that might have happened to him during his time in there?
If you're sure there's been no external event, then if it was me, I think I'd be talking to my vet.There might be some health issue affecting his nervous system.
He is only nervous sometimes.
He was in the crate for several hours. As far as I know, he was just lying there. It wasn't closed.
As far as I know, nothing happened. I would have called the vet, but it is now a holiday. I plan on talking to our vet on Friday.