"Before I begin I wanted to let you know that I have a stutter, so if you hear me getting stuck, that's what that is" "As I present you might hear me bobble or get stuck on words. I have a stutter so I appreciate your patience. "Just to let you know I have a stutter so you'll probably hear me getting stuck on some words [Optional: Thanks for your patience]." Any variation or combination of that should be good. Just don't over explain or apologize.