I'm anxious around people because I'm afraid of being judged negatively (usually by being seen as boring or annoying, both of which I loathe so much I'd rather be alone and miserable than bother other people! ).
I don't tend to experience much anxiety for anxiety's sake...there's usually a concrete cause, even if it's an irrational one. Even my anticipatory anxiety is about bothering other people. I'm not terribly anxious about appearing anxious, since my anxiety is so obvious I don't even bother trying to hide it.