I know this thread is a bit old now but just thought I would add my 2 cents worth!
My car doesn't always start - intermitent thing and very annoying. A mate of mine had a look, and in 5 seconds said it's the starter motor. He tapped it with a spanner and it started. The brushes are getting stuck apparently. It's happened about 5 times since, every time I've tapped it with a spanner and it's started fine!
Gonna book it in to have the motor replaced under warranty.