Have you introduced yourself to those around you? Try getting to class early and find a spot that is comfortable for you before everyone else rolls in. the back of the room is fine but try not to be near a side wall. (I don’t have a problem with crowded classes but sometimes even I will feel a bit weird, like being closed in on, when close to a wall.)
Spend some time warming up or relaxing, and as others join you spend a little time interacting with them. If you are uncomfortable striking up conversation just make eye contact and flash your winning smile
If you can make a connection with the people you practice with you may feel more comfortable when they are close to you.
Try sitting in Hero pose if it’s comfortable and keep your shoulders back and your chest forward. Not only do I find this a nice way to get a little stretch in before class, but the openness it brings makes it easy to connect with others.
I truly hope you can get over these feelings, for I find that once you can relax in a full class the benefits are enormous. When you get 30 people in a room the energy given off is staggering. Once at ease you may be able to feel yourself sharing your energy with others while absorbing some of theirs.
Namaste