Sounds like something like a running start. It's an avoidance behavior because instead of saying and stuttering on the sound your afraid of, you back up and try it again until you can say it fluently. I would see a speech pathologist trained in stuttering to confirm. My personal advice is to not do them as they won't always work but it'll become a reinforced behavior that could very well become uncontrolled/automatic. Imo it's better to do you best to say the sound/word and try to let yourself stutter naturally instead of fighting or running away from the stutter.