is anyone else uncomfortable with enthusiasm/fun

Maybe not an autism thing. Basically since I was a kid I've been very "mature" and unenthusiastic, I can't really express my emotions outwardly, I don't like showing excitement or joy or anything outwardly. I guess part of it could be masking too. But anyway whenever we would have class parties or games or competitions in gym class or whatever, I sorta got the sense that other people aren't real, they're like animals or characters or something, dehumanized. Other people would be having fun and I wouldn't smile or laugh at all.