The most obvious problem could be that you’re not sleeping or sleeping well enough.
We have a natural biological rhythm that helps to run all of our internal processes, and many of these happen while we sleep.
If you’re not getting enough sleep, or you have insomnia, your body is not getting this critical timing for self-repair.
Check to see if you’re allowing yourself enough time to sleep.
After that, do what you can to be sure that the sleep you’re getting is restorative and not restless.