It sounds like there is either a problem with the spark or the fuel you should start by checking the fuel pumps on it because if it isn't getting the gas it needs it cannot stay running and if the plugs aren't firing properly it won't stay running either check the owners manual on it.
There may be something wrong with the motor. Check to see if everything is alright. Make sure there is gas in your ATV as well. If the problem persists, contact Polaris.