I stuttered a lot as a kid into HS.
In fact if I didn't stutter I probably wouldn't be here. My parents took me to the stuttering clinic at Children's Hospital at age 4. They gave me a physical and found my BP was that of an adult. Further tests showed my kidney had a malformation that caused the high BP. Removed the kidney and I was fine.
Finally grew out of it by having to give talks in journal club in college and graduate school. Biden is not stuttering. Mel Tillis stuttered, Biden doesn't. He has dementia.