It may be hard at first, but stick with it and it'll become more fun and motivating. I was surprised to find out that I really love group fitness classes, especially the variety they can offer. My school offers free group fitness classes for the first week of the quarter so you can try everything they have to offer. After that, you can buy a punch card or an unlimited pass to get in. This morning I woke up at 6:00 (!? SO not my style!) because a friend wanted me to try this crazy TRX suspension class with her. That was hard, but I'm glad I tried it. If only it was offered at a more reasonable time! Just sayin'.
Three tips to get you going:
1.) As the semester starts today, there will probably be a lot of other new people there just like you. My biggest tip is not to feel self conscious in class -- there are lots of other people just as new as you. I think a lot of people avoid going to group fitness classes because they worry they'll stand out if they're new (case in point: that same adventurous friend I went to class with this morning refuses to do Zumba because she thinks she looks dumb doing it!). Don't let this stop you from going. Make sure you find out the important safety stuff from the instructor (possibly show up a little early to ask questions if you think you might need it) and then just fake it 'til you make it. Nobody will judge.
2.) I would also suggest making a few acquaintances so that you feel more accountable for going to class. A lot of the people I hang out with won't do group fitness classes, so I have another looser group of friends I see at the gym. Calling them "friends" might be a stretch, but they're people I see and maybe chat with on a pretty regular basis. Even if you don't make any "friends" per se, the familiar faces will be motivating and welcoming after a few sessions. A smile or a friendly nod could go a long way. Plus, you never know -- that person could be just as new as you are.
3.) Finally, I would suggest not just going into the class on "autopilot". That can be really easy to do, especially once you become a regular -- you just show up, someone tells you what to do, you follow along, and BOOM! 45 minutes later your workout is checked off the list for the day. BUT you might not have gotten the full benefit. To get the most out of the classes, you have to be pretty engaged. For example, use your core in the aerobics class rather than just following along with the steps (see #1 above). Make each exercise count in the conditioning class by focusing on form and quality movements rather than just going through the motions. It's easy to start thinking that if you just show up you'll start seeing results, but really the amount of effort and concentration you put into the class is what's key. You could try getting in the zone right before class with a quick warmup on the treadmill or stationary bike accompanied by some favorite tunes, that way you're not rushing in the door straight from home or another class with your mind on tonight's assignment. Or you could try logging how you felt after each class for a while to get in tune with your effort levels.
Do those classes and eat really clean and in a few months you'll be looking hawt in that swimsuit. Remember, this is a get what you pay for situation in three areas -- the more effort you put into workouts, eating right, and self-education the better results you're likely to see in the spring. Good luck today!! You've got this!