I'm a bona fid introvert and at one time may have been clinically shy, if there is such a thing. The definition of "surrounded by people" is a little subjective, but I can experience physical discomfort and maybe a bit of mind fog at two or three hours among more than a few or half a dozen people. Situationally and people dependent. Work routines with people wasn't a big issue, but work socials were generally unpleasant instantly.