Look, the car won't run if the ignitor is bad...

Most likely it is a LOOSE connection... The only way to find out is to test it... Or just buy a new one like an idiot, and when you go to put it on, maybe you would realize its just a loose connection, or something else MINOR not requiring you to buy a re-built distributor...

You definitely have a loose/corroded connection in the ignition system, especially if the problem is unable to be reliably produced (aka only happens once in awhile)...