Started stuttering as an adult

Started stuttering as an adult No one in my family stutters. I never stuttered in my childhood. Then when I was 21 it started. It would just be on occasion. It happened more each year. It's not an everyday thing, but when it hits, there will be entire days I can barely say a word. It feels painful, like my jaw and tongue are twitching while I talk. My problem is this: I keep hearing that if you don't stutter in childhood and you suddenly start stuttering, it's a sign of neurological problems or injury. My current neurologist thinks it's caused by my POTS (blood pressure drops, sometimes there isn't enough oxygen for the brain.) but it wasn't very reassuring. Has anyone had a similar experience?