I like try to start my presentation with a focus on portraying confidence. Not only to the audience, but more importantly, myself. First thing you say, say it loud and proud, shoulders back, in a wide stance. Don’t be afraid to use body language and get comfortable. I’ve sometimes tricked myself by starting out talking loud and using confident body language and it has carried. You could alert your group and/or the professor you’re closest to of your stutter prior if it would make you feel more at ease. Best of luck man, remember you are badass for even attempting this.