What's the Sears 917.xxxxxx number under the seat?
That will allow us to identify the engine etc.

There are a few different things that can cause this.
Fuel or spark.

Check the vent in the fuel cap. IF it's clogged, a vacuum slowly builds up in the tank, preventing fuel flow out of the tank. Loosen the cap for a few seconds and see if it restarts.

Fuel filter restricted- Engine uses gasoline slightly faster than it can flow through the filter. Carb runs out of fuel. tractor sits and fuel slowly refills carb bowl & repeat.

You could have a heat sensitive ignition coil/armature/module. Gets hot and quits working. Cools and it works until it gets hot again.
I suggest checking the spark quality with the engine cold and again when the problem occurs. Compare the 2.