I'm socially awkward what can I do?

Ok here's my problem in a nutshell. Whenever I'm around people I don't know very well I get all shy and look down and my lips do this really weird thing where they kind of move awkwardly. But when I'm around my small circle of friends this doesn't happen at all. I have been informed of my weird lip movement by my friends when I'm around unfamiliar people but I have no idea what to do about it. Can someone help please?