shut downs

[castro]

I have a 1991 240SZ 2.4L.
Just lately when driving my car justs shutd down. If I let it sit for a hour or so it will start right up. I have fuel ( no vapor lock ). I can drive it for hours and nothing, then I can take it for a ten minute spin and she will shut down. Like the car was hit with a pulse or something.
Right after shut down I found no voltage to the pickup coil, then all of a sudden its there and she starts up..Any ideas out there????