I have the same issue. My advice probably isn’t appropriate for a corporate job but has helped me with my career in the military. Get angry. Rarely do I stutter when I force myself to get aggressive and use my command voice to brief a group of people. Doesn’t work very well if you’re having a casual conversation and don’t want to look like a massive tool. But it works in a pinch if you really have to get something out and can’t block or else everyone will look at you like a bumbling idiot.