Mine ended up being diagnosed as Long Vaccination Syndrome by a neurologist. He thinks I was teed up by the Covid vaccine, then knocked out of the park by a Tdap booster. I did not have an initial reaction to the original 2 shot series of Pfizer vaccine back in April of 2021. I just felt a little dizzy and off (orthostatic hypotension) for the next year. I got really ill 90 days after the Tdap booster in August 2022. I saw every doctor in the book. Cardiologist, endocrinologist, dermatologist, opthomologist, pcp, rheumatologist, gynecologist, etc (yes, I was having issues in every area of my body). All my tests came back normal. I had POTS (postural orthostatic hypotension) for about 1.25 years. I just started to feel normal about three weeks ago. The last 1.25 years of my life were hellish. Google POTS and see if your symptoms match. The neurologist also told me that he really didn't know what was wrong with me and Long Vax was his best guess, but it makes the most sense. I had every test on the book: heart echo, rheumatology test for autoimmune, looked at thyroid, tested for pituitary and adrenal tumors, brain scan, etc. All clean. Oddly, the one thing that helped was a supplement sold by Lam Clinic out here in So Cal. They used to sell it online, but I don't see it anymore. I think you have to have an office visit to get access to their supplements now. But it was vitamin C based and vitamin C is a cofactor in making things that calm down your system (i'll look for a better explanation). Vit C you can get on your own and try if you want to see if it helps. The one thing I deduced on my own was that when I would have a high heart rate episode, it would last about 3 minutes. I think mine was a high dose of adrenaline that was released by my body, because that's about the length of time ir takes for your body to process it and get more back to normal. Get a fingerstick glucose kit and next time you have high heart rate, test your blood sugar to see if your blood sugar is not too low. Your body will send out a burst of adrenaline if it is. Sorry this is all over the place, typing on my phone and can't scroll back to see what I wrote. Hope you find a solution/get better soon!

I found the link to the supplement that I used. The formula has changed and I haven't taken it in this new form yet. That being said, it is heavily vitamin C based and that's much cheaper, so if you are interested, just maybe try vitamin C you buy from the store first.
https://www.supplementclinic.com/Adrenal_Stress_Control_by_Dr_Lam_p/662425055326.htm