Muscle Fatigue, Shaky Joint Movement...no loss of strength..

Hello,

For the past few months I've been experiencing some issues regarding my muscles/joints but I have yet to get answers even after seeing a neurologist and having multiple neck xrays.

One of the most noticeable issues at the moment is with my muscles in general. I find my muscles tire and fatigue very easily. Usually during repetitive motions like brushing my teeth (arms tire out), chewing food (jaw tires out), scratching my dogs belly (fingers tire and cramp). I used to go the the gym regularly and I would notice after a few dumbell curls my forearms would tire very easily and shoot down to my fingers which would cramp right up until i put the weight down. Muscle cramping in general seems to happen quite easily.To this day however, I have never noticed a decrease in strength, just overal muscle stamina seems to be decreasing.

The other issue I have noticed is difficult to describe. The best way I can explain it is this, lets say I raise my shoulders up, like a shoulder shrug. When I begin to release my shoulders in a slower or controlled motion back down into their resting position they stutter or shake as they come back down. It's very difficult to being them back down in a fluid motion. I notice this issue with other joints/parts of my body as well, but none are quite as noticeable as my shoulders.

My shoulders/upper arms seem to be my biggest problem area. I notice muscle fatigue there the most as well as that shaky, non fluid motion.

As mentioned I've seen a neurologist, and he couldn't find anything wrong with me. He did some tests in and around my wrist area and stuck a needle or something similar in both my thigh muscle and arm muscle and said all tests showed no issues. He suggested I take a break from the gym which I have for about 5 months now, but I'm not noticing any improvement. It's probably also worth mentioning I rarely do cardio at the gym and for the past two years have been very inactive, spending 10+ hours a day sitting and then another 7 or 8 sleeping. The other thing is that despite this inactive lifestyle I'm not overweight and in fact still look very much in shape.

Does someone have any clue what this could be? I struggle with pretty serious anxiety and have immediately jumped to the conclusion that this could be Parkinsons, ALS or MS. The stress and struggle with these thoughts have been keeping me up most nights and I need answers. If this is something as simple as lack of cardio, proper excercise or proper nutrition it would allow me to calm down and begin making changes for the better.

If someone could provide some help that would be greatly appreciated.

EDIT: sorry, forgot to mention I'm Male - 32- 6'3 - 198 lbs.