Most of my episodes are related to position or to lifting. Lifting shifts things around internally and some have suggested that that puts pressure on the vagus nerve. It sounds like tennis is a very specific trigger related to position or motion as well as exertion and heat.

Heat is an important factor too. My daughter nearly faints in the heat and her heart is being evaluated. It dilates blood vessels and may lower blood sugar, which I guess would make the heart work faster while at the same time you are exerting yourself. This happens to her while just walking and she vomits too.

My afib has not progressed in 10 years. I think I am lucky and am sure it will at some point. I drink low sodium V-8 and take magnesium (as I said) and eat early. I hope you can avoid medications and ablation (for now) by avoiding triggers. What happens if you stop playing tennis? How about pickleball!

@gloaming provides an excellent list of possible triggers and I would add lifting or tennis. and exertion in hot weather! Gas/belching also can trigger me probably also due to pressure on the vagus nerve. I stopped one episode with Gas-X!

Have you had a stress test? It would seem that might clarify things along with a patch monitor for a few weeks and an echocardiogram.