You could possibly have a psychological stutter like I do. I literally just answered the door for a delivery and when asked for my name I responded perfectly fine. He didn’t hear me and when I repeated myself I imagined myself stuttering. I then proceeded to stutter like crazy and it was pretty embarrassing. Wish I could re-do the past 10 minutes of my life. Anyway, sometimes when you’re excited or stressed it can cause you to stutter more than usual. Just try to remember it isn’t your fault no matter if it’s psychological or not.