Shyness Support Group
Shyness is a feeling of insecurity that certain people experience while being among others, talking with others, asking favors of others, etc. The initial cause of shyness can vary. Scientists have located some genetic data that supports the hypothesis that shyness is at least partially genetic.
Anyway, for you, who cares what they think? They obviously have the wrong impression and if they want to be jerks about it, then they aren't worth your time.
Try practicing saying hi to people first, though, because other people might be like you and not want to say it first. I get a sense of relief once I just blurt it out.