I was also having trouble with heart palpitations and a slightly elevated heart rate after getting covid last summer (late June 2022). My heart rate would elevate more than usual after eating, when laying down, etc. My cardiologist said it was autonomic dysfunction caused by long covid and didn't have anything to recommend besides staying hydrated and taking electrolytes. I did that but it didn't seem to help. Then at the advice I found on one of the Mayo Clinic blogs, I gave up sugar and alcohol; that helped a LOT. I also started seeing an acupuncturist and herbalist who prescribed me Chinese herbs and taking those also really calmed my heart down.