I have a 91 Accord EX Auto trans. wagon w/186k on it that will start/stop/start/stop as soon as I release the key each time it starts. It has a new main relay and updated ignitor(coil) rotor & cap w/10k miles on it. My next thought is the ignition switch. Does the wagon have a different switch than the sedan. I'm losing my sense of humor on this car.

 

Sounds like the electrical portion of the switch is worn out.

 

ignition switch would be my first and only guess