Thanks for continued input. Yes, I have been up and around as much as possible, and trying to stay active and not lie down more than necessary. Even at its worst, I was up more of the day than lying down. Just do that if I hit an exhaustion wall, and then only so long as I need to.
As to the cause, it’s all come about during this just-over two week period since Jan 6, and the fatigue really only since sleep deprivation mixed with covid. So I’m pretty sure it’s mixed in there somewhere. I guess if it lingered and lingered, it would necessitate looking for more. But the onset was definitely recent.