The instant it stops toss a teaspoon of fuel down the carb.
If it fires right up and burns off the teaspoon of fuel then you have a fuel supply problem.
Either in the carb or the tank.
Debris builds up in the tank and forms a plug so the pump can not keep up with the engine.
A blocked tank vent will do the same thing , try mowing with the cap loose .
Get back & let us know what happened.