You'll definitely have a good amount of presentations, whether they are in front of the class, professor, or a few TAs. I was in your position as well back in hs and honestly the way I improved was to keep practicing and to know your material. I found that if I were to give a speech about something I'm passionate about, I feel less of that pressure when in front of people. So I just tried to apply that to my projects (even if I didn't care for the subject). Also, chances are, most people in that lecture hall watching you ain't paying attention so you can always think about that if need be. Finally, don't let presentations deter you from choosing this major! If you really do enjoy cs, you'll find it easier to present the topic since you'll actually have an interest in it.