I second the fuel relay as the problem. If so the problem is caused because a crack has formed on the printed circuit board of the relay. It is repairable if you have a solder iron. Pull the relay (black box about size of pack of cigarettes), pop off cover and examine back of circuit board where the pins are soldered to the printed circuit. If damaged you will see a fine circular crack in the solder around one of the pins. Drop new bead of solder on the spot and you will be running normally again. The pin will be attached to one of the heavier coils that are mounted to the circuit board.
The problem occurs because the crack makes intermittant contact... depending on temperature, and forces of the car's motion etc.

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Earl



1993 190E 2.3
2000 Toyota 4x4 Tundra