There are a range of tachycardia/arrythmia that you can have since birth that may not show up until you’re older, or get triggered by certain meds or nutrient deficiencies (things like potassium).
I wouldn’t ignore this for a minute longer. Maybe just walk into urgent care and ask if they’re equipped to check it out (basically EKG). I know my urgent care is.
If they aren’t equipped, then go to ER.
But please don’t sit on this any longer. Some arrythmias are fairly benign, but if it’s happening repeatedly, it will eventually cause tissue damage that you don’t really fully recover from. Plus you don’t know if yours is benign (and most docs would say arrythmia is never benign, even if it isn’t killing you in the moment).
That’s the key.
That said, I’ve always bought ~2 year old phones. They usually have batteries at 85% life (or more).
I haven’t had fast charging hurt one significantly yet, and I’ve used it a lot on some phones.
Of course, I avoid using it as much as possible. I use a slow charger (1A,max) overnight and it’s on a timer. On rooted phones I use a charge limiting app.