it happens to me specially while speaking out loud in class. what helps me is breathing, even between words, talking slowly like slow pace ( i think talking slow is better than stuttering) and tapping my hand on my thigh or the chair im sitting on.. (your mind gets distarcted as it divides the attention between two things) and not being hard on myself, plus faking confidence. fake it till you make it. these all are basics but it helps so thought about sharing it :)