[Broken_Hippo]

I'm similar: I find large groups easy, small ones more difficult. I always think it is because the people in large groups are anonymous.

This is, as you say, social anxiety. And you might be able to get better with some practice. Local theater, choir, or other hobbies might prove to help or simply doing things that get you out of your comfort zone more often. Basically, this is just training yourself to act differently and gets you more used to small anxiety. Of course, a lot of the practice won't have the added stress of your career so it might or might not pay off.

The other side of this might be some help through professionals. A therapist might be able to give you some spectacular tips that me, an untrained random internet human, won't know. A GP might be able to prescribe something to help with the anxiety.