1998 Town & Country

I have a 1998 Town & Country van. Periodically it will fail to crank. I thought at first that my battery was dieing but if I kept bumping the starter, It would start. Thus I thought it was the starter or relay. I checked the starter and it sounds and turns good. The last two events exhibited some unique symptoms. When I turned the switch on, the dash console lights would power up but the gas gauge would not. The engine would start but only run for a few seconds. I did this for 4 or 5 times and then the starter would not turn. It was as if the power was cut. I by passed the starter relay and the starter turned and sounded good but the van would not start. I thought maybe that I was out of gas so I added some gas and the engine started. The last event was a couple days ago and exactly the same. I knew I was not out of gas but added a couple gals anyway. The engine stated. I have had a local mechanic check but am told they cannot detect a problem unless they can check it when it is malfunctioning. The mechanic said if he had to guess, he would guess the ignition switch. Any assistance you can give is appreciated.
Buffalo