I was a very healthy, active person before COVID, then started the same symptoms about 1 month after infection-that was 1 1/2 years ago when there was little research available to doctors. Finally, I got a '21 day Event Monitor' order from my PMD; a holter monitor is for too short of a time. It was the final evidence of 'Inappropriate Tachycardia'-a heart rate disproportionate to my activity. My cardiologist tells me he is seeing this a lot with his covid patients, and not necessarily those who were hospitalized. I am now on Metoprolol for heart rate control. There is a lot of information on nih.gov, the National Institute of Health; look under COVID and Tachycardia (fast heart rate). There are several possible diagnoses-POTS is certainly one. CDC's website also has great info-you are not alone.
I kept a daily journal, documented my activity (walking at slow, normal, fast rate, climbing stairs, towel drying after a shower, laundry/folding sheets, at rest, getting up and walking after sitting) and heart rate to show the data to my PMD. My heart rate went to 150 washing my hair!! My EKG, Stress Test, Echocardiogram, a test that had me riding a bike and hooked to a monitor.... were all "normal". I am an ER Nurse with 40 years of experience and ran a half marathon for my 60th birthday. I have a lifetime of knowledge about heart rates. It took a LOT of persistence to get the Event Monitor which objectively confirmed the symptoms.