Before you go pulling it apart check this thread:

http://www.poolforum.com/pf2/showthread.php?t=4800

There really are no dead spots in motors like this so I'm thinking it is the starter switch contacts. The starting capacitors usually fail open or shorted and don't usually fix themselves, but I guess it is possible, but unlikely, for it to go intermittent. I'd start with the contacts. It is something that is easy to try. Would be nice if you could pull the cover to expose the contacts and start cycling power to see if you can get it to not start, then tap the contacts.
Hope it is something simple.
Al