I have been getting the well documented "Hot starting problem" for a number of years. It will start when cold and when at full operating temperature. But if it cools a certain amount, it will not start. When it cools further it will.
No fault codes are reported (Bavarian Technik)
Much has been written about the solution, fuel pumps, relays, injectors etc. In my case I have identified it as the cam position sensor.
It failed three times last week. Each time I cooled the sensor using a can of Maplins Freezing Spray (use gently as this is powerful stuff). On each ocasion the engine started first time. Experience has told me it would not start for at least 45 mins without this treatment.
So convinced am I that I have just fitted a new BMW part (£88!). I expect this to be the end of the problem, but I will report back if it is not.
Ok it is now May 2012 - NO futher problems since replacing the cam position sensor.