Anyone have LC energy crashes and dysautonomia without POTS or PEM?

Just curious how common this is.

I don't have PEM. I can exercise. I can exert myself almost as much as I could before COVID (probably 90%) and would not cause me to crash or have to restrict my activities in any way. I can do this for weeks at a time and be fine. But sometimes I have PEM-type crashes. They come out of nowhere. They are totally random. They are severely disabling and leave me bedbound usually for a few hours but sometime for up to a day.

I don't have POTS. I've been tested for it a few times, including with a tilt-table and do not have it. However, I have dsyautonomia symptoms, including severe heat intolerance, occasional dizziness, coat hanger pain and other symptoms. Other than the heat acting as an obvious trigger, this also seems to be completely random.