There are a couple of words that describe a lot of similar behaviors. I’m going to try to define them and likely will fail, but I wanted to have a post to refer to each I use those words.
Social Anxiety. This is a feeling that something isn’t right– not the same as the terror of watching a frightening movie, or the fear you feel at great heights, but that wrenching tighening of you will to speak, interact and god forbid sing when people are around, especially around strangers.
Social Phobia. Gregarious extroverts might have a social phobia, which can often be super specific, like being afraid of using public restrooms, giving a speech, fear that people will see your shaking hands. Agoraphobia is somewhat related. I’m not afraid of crowds, I’m
Avoidant Personality. Someone who has a bias in all they do to avoid other people.
Introvert. Best defined by what it isn’t. Everyone who isn’t gregarious.
Anxiety. Something bad might happen and you are suffering.
Fear. Something really bad is going to happen, you know it and it makes you want to run.
And as I read in Coping with Social Anxiety, there are a lot of reasons why people might not socialize and there are a lot of instances of fearful, anxious, introverted, avoidant, phobic behaviors that happen in the lives of perfectly average people.