I have lost that fear over time but giving a speech in high school was my idea of a week of hell in anticipation of having to do so. For me, it had to do with standing up in front of the class. I was fine with raising my hand to give an answer to a teacher's question, and I was fine with going to the blackboard and doing math. But facing the class and speaking was treacherous to me. The day I had to speak in my senior year, I just got going on the speech and suddenly the fire bell rang - and we all filed out of the room in the fire drill. After we got back, I finished the stupid speech.
I lost my fear when I was in landscape architecture school. We had to stand up in front of the class, show our designs or plans, and then take criticism from the class and the teacher. I survived the first few times and then actually enjoyed the process. I think that had to do with my then fairly advanced age (40) and improved self confidence from the days when I was a teenager. I've since spoken at a lot of city meetings and not been fearful.
There was one time when I regressed - in order to pass our state board tests, we had to be examined by a set of architects regarding matters of public welfare relative to our design work - this would be after we had three days of written testing. I remember sitting in the room where we all waited, and that I turned cold, my hands ice cold, probably my knees shaking. Turned out fine, and I knew I passed as I left the room just by the look on the examiners faces.
Anyway, I think this kind of fear is fairly common, and that it is centered on self awareness, as much shyness is.