I have similar symptoms and of course nothing was found until one neurologist suggested doing genetic testing. I found out I have a rare neurological disorder called Hereditary nerve Pressure Palsy. As I got older it got worse and started affecting my bladder and bowels, all my muscles in arms and legs and I get lots of internal vibrations and nerve pain and fatigue. I highly suggest genetic testing.
Good luck and I hope they find the source of the problem. It’s very frustrating!