I have the same problem where mine isn't a mental illness and it's just a bad habit. Just talking to people seems to help me and if you can't talk then I'd suggest bringing a notepad to places and writing things down. If those two things don't help then I'd suggest speech therapy. It's helped me out a lot since I was younger. Edit: Stuttering can be neurological and be caused by other things in the brain but for me that wasn't the case and it was just a bad habit. I'm not saying that all people who stutter are going through "a bad habit" though. It can be caused by many different things.