Volvo Repair: volvo starting, coolant temperature sensor, sensor control unit

Question
I own a 1989 740gl. I recently been having problems with my start up. When it is cold it starts up and as long as I am driving it will continue to drive. But once I cut it off I have to wait at least 15-20 minutes for it to start up it will turn over but it will not catch and start. I had some recent work on it. A new distributor cap,rotor,spark plugs, coil and a new ignition module. Please I need some help figuring this out as soon as possible

Answer
it could still be many things.the only way to be sure and not to guess and waste money.would be to check the car for fuel and spark at the time it does not start.this will at least give some direction to check.it could be a bad fuel pump relay,radio supression relay,rpm sensor,distributor,coolant temperature sensor,control unit.it will really need to be looked at for a proper diagnosis.