I've had mine catch on fire twice.
Hot day, dry grass, I shut it off and was going to get a drink, just happened to look back and there were flames coming up from near the front. I had parked next a hose so it only took a few seconds to put it out.
After that I always had a hose ready and would park next to it, then step back and watch for a few minutes.
It happened again about two years later, same scenario.
After the first time I always waited until it had cooled off before putting it inside.
I had a large area to mow, it took a least couple of hours if I did it quickly, so it had plenty of time to build up heat and collect dry grass.