My starter works most of the time but after driving and stopping the starter turns over and over without cranking. Waiting 20 minutes and it cranks.

By posting exactly what is happening with your vehicle! .. The starters only job is to CRANK the engine so it may START ... You can CRANK an engine without STARTING the engine .. But you can not START an engine without first CRANKING the engine .. Engine CRANKS ok, but does not START? .... Engine does not CRANK?