Just be open with your clients so they know what to expect and to be patient. It wouldn’t bother me one bit if my trainer stuttered. Especially if he told me in the beginning of the session that he may stutter and to just be patient, that’s totally fine! Doesn’t mean that you don’t know what you’re doing. As a teacher who gets up in front of 20 kids and a handful of adults everyday, as long as you’re good at your job and have good intentions, no one will care. Especially if you’re open about it. People will like you for the effort you put into your job, not how you give instructions. Throughout my schooling I was always nervous about going into my field with a stutter. How can a person with a stutter teach kids? Well it was silly of me to think this way. I’ve had multiple people tell me they don’t notice my stutter, or if they do, they tell me that my personality and passion makes up for it tenfold. Don’t let this stop you from doing what you want! Best wishes!