What I don't understand with him is why, when he doesn't participate at all in the motions or singing that goes along with the songs at preschool, just a couple times he has spent the whole drive home singing them complete with the hand motions while I listen in shocked silence. He seems to enjoy them so much when he's singing them, I'm confused why not at preschool. He's not shy so ?
My DS does that too, and I have no idea why.

He was like that with singalong TV shows as well. I guessed perfectionism?