I have two (2) 652R John Deere stand on mowers that after running a while and turning them off, they will not restart. You turn the key and absolutely nothing happens. There seems to be a heat or timer issue as after 15 to 20 mins, they will start with no problem. I know there are switches everywhere, including PTO, brake handle, and the step, but they don't appear to be related to this issue. The John Deere dealership just said bring them in and we'll check them out. I'm not sure how they would diagnose this sporadic issue. Any insights anyone has would be appreciated. Thanks,