My van runs perfectly, then without any rhyme nor reason it will die. When this happens, I pull over, turn off the ignition and then turn it back to run. If the check engine light comes on it will start and run perfectly again, if it does not come on, then I must turn it off again and wait. Eventually the light will come on, and it will start. The computer has been replaced (2x), several relays, plugs, wires, cap, rotor and coil, ignition switch, battery, o2 sensor, local mechanics baffeled. Computer analysis reveals nothing. When disabled(not running) there seems to be no power to the engine electronics. Help!

Sounds like a bad connection somewhere. You will just have to hunt it down. Copying from another answer today:

Intermittent electrical problems are a big pain. I fought them in my truck for over 20 years. Finally, a year ago I removed the fuse box, removed the riveted contacts, soldered the joints, and put it back together. It has run better the last year than it has since it was a few years old.