Yes, I know what you're talking about. First, there are many people I don't feel like getting acquainted with at work and even looking them in the eyes and saying hello when we pass at the coffee machine or in the lift is difficult (I'm talking about people from the department that I don't work with but see almost every day).
Then, there is always this fear of looking bizarre, like they're going to see my DP. The most horrible part is when I have a conversation in "automatic pilot", I emerge and realise what's going on. Usually, the other party hasn't noticed anything but it makes me very uncomfortable.
Also, it takes me a long long time before I feel comfortable with new acquaintances usually. I don't make friends easily.
What is your experience of social anxiety, mate?