I just spent 2 weeks at Mayo Clinic in the post-Covid clinic. My main symptoms are crippling shortness of breath, fatigue, memory issues, joint pain and headaches . I have had so many tests. They found cytokine abnormalities and have referred me to their post Covid program which I will start beginning in February. Essentially it’s that the fight or flight response of the sympathetic nervous system doesn’t shut off like it should, and causes big problems. The treatment is to try to get the body out of fight or flight, to let the parasympathetic system take over. Relaxation techniques, meditation, rest, paced return to activity. I’ll post again once I take the course. Hope this is helpful information.