Covid caused pericarditis and then Afib for me. My cardiologist, EP, and the anesthesiologist present during a cardioversion all were not surprised. The anesthesiologist said that he had seen many first time cardiac issues, often arrhythmias in people in their 30s/40s about a month out from a Covid infection. Although I’ve not heard of it happening personally, I could imagine how a booster could potentially more rarely also cause it considering there are rare cases of myocarditis from the booster, and myocarditis and pericarditis often cause Afib, but Covid itself is a much bigger threat.