Have had "localized" fatigue in my arms, had to wait it out, never found a solution and it wasn't caused by compressing anything which often happens to my legs and causes a sort of just tiredness and numbness and pins and needles feeling. My arms just felt tired and moving them seemed to take so much more energy.
For crampiness these help me:
1) had your vitamin D checked lately? The deeper and more in the bone the pain feels the more this might be related. Mine was low and resistent to going up so I supplement pretty high every day.
2) Magnesium supplements tend to help crampiness for me, of the charlie horse variety - doesn't help the period variety for me which is more "nerve" like but still crampy.
3) potassium from foods - potato, banana, orange juice there's tons of others... Potassium I do not supplement for because there are bad consequences to "ODing" on it. I prefer food sources because I feel like people can eat 10 potatos a day and not OD on potassium [some people do it's called the potato diet haha].
Magnesium, D, potassium, and calcium sort of work in conjunction with eachother in some way and can even inhibit eachother if taken at the same time I think- or at least other medications/vitamins. There is some kind of balance that magnesium and potassium especially are supposed to have with one another.
The defining thing about these being related tends to be that they occur over long bones/muscles... So shins, calves, forarms, upper arms, and back mostly.
You can also try topicals, some people really like:
1) capsaicin cream
2) arnica gel * This is the only one I have used it isn't helpful for deep pain though.
3) magnesium cream
4) I have also had some luck with essential oil muscle rubs, the one I like came in a squirt pen, but it leaked and/or I lost it.
Gently stretching or massage can help sometimes depending on the pain. Warm/moist heat helps me a lot, some people like epsom salt baths but if you feel you can't trust your limbs to get you out of the bath or support you up- maybe don't go for that. If you can't do baths try a heating pad with a well rung moist towel/ just don't get the electrical parts wet.
With that said, your problem could be entirely unrelated to any of this. Keep track of it and if it gets worse or lasts more than a few days it might be time to see a doc of some kind or at least call the on-call nurse for one of your docs and see what they think.