I'm 21.

Whenever i'm with a friend (doesn't matter how close) i can be as goofy/weird have the confidence of a million men combined(doing stupid things, approaching girls, etc). But, I can't seem to do any that alone. Don't get me wrong I can do many things on my own like gymming, grocery shopping, going to a bookstore, studying, my hobbies, etc etc but I can't seem to bring out the fun in myself when I'm alone.

Thoughts? Any older RP guys gone through this? How can I fix this?