Yeah, it's normal. But do it often enough and you'll get used to
it. I used to be afraid of dogs and injections, life has a funny
way to screw me up, I ended up being an owner of a really nice dog
and sent to become a medic, believe it or not, it kills my fears.
As for presentation, do it often and you'll not feel so bad
anymore, but hey it's easy for me to say rite coz i am not you, I
was also somewhat nervous during my last seminar. Tell you what, do
lots of preparations for your presentation, get some interesting
points that you think the audience might not know about, and since
I am no presentation expert, I suggest you go library grab some
books to get tips on doing good presentations.