Know your topic and focus on the knowledge you are imparting. That's all that really matters.
I used to have trouble looking all freaked out. (speech class in college) The teacher said to just keep pushing forward and ignore how freaked my body was. Ahaha!
I got over it when I had to do a speech to all the co-ops and my boss at Goodyear. It was sooo stressful that I had to find a way to overcome it.
I think INFP could be awesome at public speaking but like everyone else would have to warm up to the idea.