My 1994 Volvo 940 stops running after a few minutes any one knows why?

My 1994 Volvo 940 cut off on my wife on her way home it took 4 starts for her to make it home.I have changed the spark plugs and checked the fuel pump and there is a steady flow of fuel .Usually it starts right back up but it stops after about 3-5 minutes.Sometimes it may take hours before it starts again.I would appreciate any help any one has to offer.My Volvo is non turbo.|||There may be a problem with the car's computer. If you are not getting a check engine light, then that may be the case. It could also be the fuel pump relay going bad and is switching off the fuel pump.|||Thats a simple one because its a volvo :) sounds like it could be an electrical fault with the distributor. GOODLUCK|||sounds like its a coil or another eletronic part when it gets hot it dies