Zero Turn Mowers

I have a 2 year old M61 zero turn mower I bought new in April 2015. I have been having an issue in that the mower runs great when I am out cutting. As soon as I shut it off after cutting for an hour or two, I can not get it to restart. This has happened over a dozen times now and I try not to shut the tractor off until I am finished my work for the day. Yesterday I shut the mower off and went inside for a bit. After 1 1/2 hours it still would not restart. I try to engage and disengage all the safety interlock features like the blade and the parking brake and the handles but no luck. Sometimes it will start back up in 10 to 15 minutes. One time I had to leave it outside overnight. What can I have the dealer check to resolve this issue?