What to do about it? Teaching IS about being up there in front.
If you feel you have stage fright then it is a good idea to do some practice teaching. Most of us do feel some anxiety when teaching a new class with students you don’t know. Even I do, with 25+ years experience, it is still there! Another way to deal with it is to be SUPER prepared and practice in a mirror. Practice a lot. It can seem silly, but it does work.
If you are a naturally shy and quiet person (I am) then the preparation helps. Try to view teaching as theatre.
Practice some disciplinary redirection, so when it happens, you are ready for it and can be relaxed as you do it. It will happen if you are NOT prepared, probably not if you are! Life is that way.
Relevant language games with the target language will help a lot as when your students and you are laughing and enjoying what you are doing, tension/anxiety/fear tends to melt away. Even do too much of it at first, don’t feel like everything has to be perfect. No one ever died from an imperfect class. That’s one of the best things about teaching. No one gets horribly hurt by an error on your part. So do a lot of games and then trim it back as you feel more comfortable. Laughing (and students in most countries LOVE to laugh) is a magical antidote to stage fright.
This issue is VERY beatable. But I personally know how much anxiety it can create. Go with a lot of games to get started. Games also quickly build a nice rapport with your students. There is a balance though if you want them to take you seriously. But worry about that later. Just have a good time first. It’s okay to spend a class or two on YOU, so you can be a SUPER teacher later. If your class is part of a teaching practice, then be sure to let your observing teacher know that is your plan or even tell them not to watch for the first 2-3 lessons so you have no concern about being judged. Just go with a plan to enjoy yourself and have some fun. Why not?
Tip #1: Teaching can be so much fun and so rewarding. Do what you need to do to make it a productive part of your life.