I’ve experienced the same and paired with my anxiety, I get really uncomfortable it interferes with my day to day life. I’ve visited a couple cardiologists, both well regarded, and been told it could be inflammation and to ignore it unless its painful and to get more fit (BMI fine, but a bit sedentary). But I feel the medical community is lagging behind in this regard, sadly. Oh, and masks didn’t make much of a difference anecdotally here.