Have your battery load tested or just buy a new one if it has never been replaced. You may want to test your stator also as it sounds like the battery is not charging when running. I've not owned a Polaris but your issue definitely sounds related to the battery/charge.

 

First off check battery connections plus check that it's charging around 14 volts back to the battery.Sounds like the 20 amp thermal circuit breaker is crapping out on you. They can kick on and off if over heated,corroded or just worn out.Then kick back on when cooled down a bit. Should be in a plastic pouch on the main harness located up from the battery.Check for power on each side of the red wire on the pouch when it dies. If power isn't going through,slice the pouch open and replace the breaker. The parts break down doesn't show its location but lists it along with the 10 amp fan circuit breaker. Item #2. https://www.partzilla.com/catalog/po...-ab/electrical You can get these at any auto store for about 8-10 bucks.