1999 Oldsmobile Alero Car acts different when hot or cold.

Whenever my car is cold is its going to get, it cranks up great, not even a hitch. But whenever the temp hand is at its usual halfway mark, and I continue to cut the car off, it refuses to crank back up! The only way I can drive my car again after its hot, is to let it sit a while, usually about an hour or so, until its cooled off enough to where it'll crank right up again. Whats wrong?