My pre-crash symptoms include shortness of breath, dizziness, unsteadiness, mild headache, etc. Also, as I already posted, I've learned that I can mitigate the crash by lying down and performing deep breathing. Also, I try very hard to limit what I do in a day.

Does a “long haul specialist” really exist???
I have been to numerous doctors at Cleveland Clinic and all appear long hauler phobic since we don’t fit in with obsolete categories of symptoms and tests they have used to diagnose pre-Covid era. When tests come back within range, they pass you down the line...
The field is too new and if they are not paying attention to the current research, they haven’t got a clue. Sad but true.

I have been noticing that I do get dizzy and a headache. Prior to crashing. Then I am tired and sleep for a few days qhen I overdo it