Wow its interesting to see that you described it exactly like I would. I am in the same situation, if I start good I will get comfortable and carry on, but if the stutter starts from the beginning then it will not stop till end. When its my turn to present I feel like giving up and not presenting because my anxiety levels go so high, my heart feels like it will go out of my body. Hh its hard to describe it all, I could write a book about this cursed disability, its messing up so bad with my mind.