After driving my bike,when the engine is hot,I will stop and shut down the bike.When i go to restart the bike within a minute ,the starter will engage then stop and will spin again and the bike starts
Usually on Harleys when the engine stops, one of the cylinder might have both valves closed.
The engine is cooled by the air stream as it moves through the air.
When stopped, so does the air stream.
While the motor IS cooling down while stopped, the air trapped in that one cylinder is actually heating up from the residual heat in the cylinder, combustion chamber, etc.
Air will expand when heated (elementary school science 101).
IF the air can't escape (because both valves are closed), it will compress when it runs out of room to expand, which will make the engine harder to turn over, until the exhaust valve opens to release the trapped air/pressure.
Newton's First Law of Motion states that an object at rest tends to stay at rest (basic physics).
Where this applies in your case is when the engine is stopped, it takes quite a bit of energy to get that (relatively) heavy crankshaft/flywheel up to full cranking speed.
So, here are your choices:
Install a more powerful starter (more Kws)
Install compression releases
Learn to live with it