I'm an INFJ and this thread seems to be about INFPs (a type I don't know a lot about) but I wanted to throw in.
I am not a shy person either, and I too made a living being on a stage as an Improv performer. All my MBTI tests always came back with INFJ and it confused me because I associated 'introversion' with 'shyness', as I think a lot of people do. My family is comprised of all introverts like me, but the rest of my family is pretty much comprised of hermits. I'm loud at times, opinionated, and genuinely like being with people. Very confusing!
I saw an illustration in an MBTI book once that made things so clear to me. It was supposed to illustrate the main difference between introverts and extroverts. The figure of the extrovert was depicted with a wire coming from himself that was plugged into the world, whereas the introvert was depicted with the wire plugged into himself. Basically saying "An extrovert gets their energy from the people and world around them, the introvert gets their energy from within themselves".
It made perfect sense to me. I get a kick out of people and crave companionship just like anyone, I just crave it less, it takes more out of me, and I need alone time to recharge. I'm not shy, I just don't get energy from others as much as I do from my alone time. I might spend a whole day with people I love or I might spend a day performing, but it will drain my resources and I need quiet time alone to refill the energy I need to do it all again, if that makes sense
An extrovert might be shy, but they will get their energy refilled simply by being around people. I know a couple of people who have a painfully hard time talking to anyone at parties or gatherings but want to go all the same. They'll come back feeling good and energized from being around others even if they spoke to no one.
I went on a little longer than I intended, but I hope this was perhaps helpful