I'm kinda in the same boat. I am starting grad school, and have always had issues w/ presentations. When I stutter, it's not always consistent. Personally, I don't like to tell anyone about it, because part of me is hoping that I can get through my presentation in a smooth, inconspicuous way. But then it happens, and it becomes really obvious...and then I feel like I owe an explanation to those who are listening. It becomes really uncomfortable on my end because of this . I know I should announce it early on, but getting to this point is scary for me, still.