Oldsmobile/Buick Repair: after driving will not start, oldsmobile ninety eight, crank sensor

Question
1994 Oldsmobile Ninety eight regency 3.8 engine.

will drive car for different times all within 30 minutes. Out of 10 times I get in my car it may do the following once or about once every 2 weeks.  I'll drive the car for about 20 minutes get down for about 10-20 minutes come back to the car and it will  not start. The engine turns without any problem, starter and battery are great, it just will not turn over. If I wait about 1 hour or 2 come back the car will start right up. I have replaced the fuel pump and filter for this reason 6 months ago.  All went well until the last two weeks.  This has happend twice in the last 2 weeks. First time just keep turning the engine over for about 10 minutes until it started.  The 2nd time drove for about 10 minutes went into subway,  ordered to go, came back to the car and car would not start, tried for about 30 minutes and nothing.  Left the car at Subway returned the next aftenoon and car started right up.  No check engine light, had it checked any way and nothing comes out on the check engine diagnostic check with pep-boys.  It will happen again just dont know when.  
Had pep-boys have it for a full day driving around but car never did fail.  confussed.  

Answer
HI RICHARD.WELL SPENT SOME TIME AT PEP BOYS .THIS IS A COMPLICATED PROBLEM.ESPECIALLY SINCE I DON,T KNOW ANY OF THE SPECS ON THE CAR BUT SOUNDS LIKE A CRANKSENSOR PROB TO ME JUST BY THE WAY YOU EXPLAIN .THERE IS NO WAY OF CHECKING IT WHY THE CAR IS RUNNING OK.JUST TRIAL AND ERROR.DIST MODULE OR CRANK SENSOR.HOPE THIS HELPS PLEASE RATE MY HELP TY BILLYMAC