No Start Mystery

[drew3007]

I have run into a lot of problems with Boxters not starting but this case is a mystery to me. To start, the DME and electronic portion of the ignition switch has been replaced. The problem happens only once every 2 weeks or so when the car starts fine, is driven, to say, the store. No problems. Come out of the store and try and start the car and it cranks over well, the engine turns but refuses to fire. If the car is left alone, for sometimes hours, it will turn over and start immediatly. The car will not stay broken long enough to get to a shop for diagnosis and in the past has been towed but starts immediatly once off the flat bed...of course. Any thoughts and ideas would be greatly appreciated. There are of course pleanty of things it could be but it is impossible to test unless it stays broken, so I am just hoping for past experience here.

Side note: The car is in California, so weather and temp are almost certainly not the cause.

[TECH911]

Just as a question. Has the inside of the car ever gotten wet? How many miles are on the car?