I did feel the same every time I had to do a presentation. But it was all gone after I’ve done it. The source of my stress was mainly the anticipation, since most presentations were by alphabetical order and I’m one of the last ones. I found myself slowly getting out of breath the longer the presentation went. My solution was to talk with the professor the first day and ask to go first whenever possible. I would also place some media in middle of my presentation to catch a breather.