Why am I so nervous about meeting new people?

When I’ve gotta meet new people because I’ve either gotta do a uni project with them and I just know the name of them and just seen them in my class, I’m so nervous to actually meet and have a conversation. Also if it’s someone offline that I have been speaking to, that I might have seen before but never had a proper conversation with, I’m soooo nervous! I mean I legit will have a anxiety hour before the plan, go and look out a window or around the corner to make sure they are there and work myself up to going over to them and genuinely freak out. However when I meet with them, I change and completely just don’t care after a while because I get comfortable with them