What engine / model #s would be helpful. First guess is the ignition coil is on the way out- especially If you have a Tecumseh engine. Some Briggs have different issues that are more common to them.I like to cover my bases knowing the fuel is fresh, carb clean, fuel cap vents well, and has a new spark plug 1st. You could pop the air filter and give a shot of carb spray when it is in not starting mode and see if it wants to fire up when you pull it.

I had a similar problem on my neighbors lawnmower. Thew blade was so dull it made the engine get hot and would not start after the bag was full.
I would suggest to do all the basics first like spark plug air filter oil etc.
Then see if you still have the same problem.
One of the most neglected things I have seen is the fins were blocked.