Even though most people know that stuttering is involuntary, an assumption I see often is that a bout of stuttering is triggered by general nervousness/uneasiness, unpreparedness (e.g. for a meeting/presentation), dishonesty, or feeling uncomfortable around the person you're speaking to. That's usually not the case–sometimes it's as innocuous as a difficult word/consonant, cold temperature, excitement/thinking faster than I can speak, or no particular reason at all, just random. Whenever the reason is emotional, for me, it's almost always the fear of stuttering itself, but rarely goes deeper than that. It can feel pretty vulnerable when people use your stuttering as a way to gauge your inner thoughts at times when there is no correlation.