I have also had the experience you relate, but from the opposite side. I volunteer as a peer counselor. From time to time our training involves practicing with other volunteers. One of us pretends to be the client and we practice our skills. I love doing it and I had no idea that half the volunteers hate it.

I wouldn't actually link it to introversion/extroversion. I am shy, especially in groups where I am unfamiliar with the appropriate way to behave. Even when I feel like I am participating often I find that I am not, such as in seminars. I need to know most of the people in order to speak. But if I'm given a role to play that goes away. As soon as I know how to make sense of my role in the group I can interact. That's why I love simulation, because I don't have to be me. I can pretend to be a certain kind of person, the kind of person who would be function well in this situation.

I would say playing is the best thing you can do. Play with ideas, ways of behaving, etc. Improvise. Join a free style dance like swing without a regimented set of moves.