It is more than likely going to be electrical. A couple of tricks to make the problem occur. Use the wifes hair drier and heat the suspect electrical components such as the ignition module, coils, etc., and see if you can cause the symptom to appear. Don't forget the connectors, in fact I would do them first.

If you have access to an electronics store, you can get a couple of cans of freeze and go the other direction. Get the symptom to occur, then cool things off until it clears. jd