I stutter when I’m alone and even in my own head I sometimes feel hesitation in my own internal dialogue because I’ve learned over the years which words I can and cannot say. There’s many reasons for stuttering. Genetics can be a factor as it’s found to run in families. Disruptions in neural processing which could even be due to differences in structures in the brain compared to someone with typical speech. The neurological differences can cause issues with motor control of speech which can make it feel like a more physical problem, some people get quite severe tics when trying to speak for example. It can also be caused by stroke, due to traumatic injuries to the brain it can cause. Emotional distress or trauma are also big factors, particularly when children are in the developmental stage of speech. There’s many different reasons. And everyone can present differently or can stutter for various reasons. Whether you stutter alone or not, try not to think about it and just focus on being yourself and feeling as relaxed as possible :)