You will have to give many presentations. In the first semester I think I gave 4-5. This semester we will probably give 8 or so. I'm a natural introvert so public speaking definitely doesn't come naturally, but I've found there are essentially three keys to giving good presentations.
1. Knowing the material frontwards/backwards/upside down.
2. Having a set outline/progression for your presentation. Even if you know everything there is to know about what you are presenting, if it is not properly organized you can loose your place/get disorganized and it all gets jumbled up. Use note cards, a piece of paper, whatever.
3. Practice out loud, even if it's in the shower or to your dog (my preferred method.)
In essence preparation and confidence.
In undergrad I usually just winged it and did well enough on tests to the point I didn't really care about speeches/presentations because I didn't really like giving them in the first place. But, if you want to be a good PT you will have to be able to teach/educate/explain to patients/families/colleagues, so you might as well work on your communication skills now. For most people public speaking is an acquired skill set. All you have to do is make sure you put in the effort and it will get easier with time.
I know we are talking about PT, but as you advance in any profession, sooner or later you will be required to speak publicly and communicate ideas/teach.
BTW. We've had professors who have been teaching for 20yrs who have stated they still get nervous when teaching, so you are definitely not alone🙂