99 Toyota Camry with intermittent starting problem: sometimes it will, sometimes it won't with no cranking

99 Camry starts when it feels like it. Usually, it starts right up. Occasionally, it will not start at all. All lights come on, but no cranking. I have had electrical checked. Mechanic cannot get the car to duplicate the problem in his garage. Does anyone else have this problem? Better yet, does anyone have an answer to this problem?