@tootall10 It is surprising how many people experience arrhythmia, particularly atrial fibrillation, when reposed at night. My sister in law is one such person.

Sleeping on one's left side is often not advised in forums where AF is being discussed. It seems to make the heart cranky.

One major cause of AF is sleep apnea. The heart never rests long because it is constantly ramping up to 120-150 BPM in order to keep its host alive when they stop breathing 10, 20,30, 50 times each hour. Sometimes for 20 or more seconds. Or they breathe poorly and this goes on for most of the night to the point where the person is largely hypoxic all night long. If you have not been checked for that, maybe ask for an over night polysomnography at an accredited sleep lab. I did, me a lifelong athlete and not a bit overweight. The result? 'Severe obstructive sleep apnea.' This report was explained to me by a third party physician not affiliated with the lab. It was his job to convince me I have a problem and to accept treatment. Neither the lab nor the physician got a dime out of me...all paid by the province, so they had nothing to sell me except to 'splain what had been found. I had to go to a medical supply seller and purchase a CPAP machine, the right model for my particular need.