Hi,
Had the same problem with my 2.5. Sometimes it would start Ok when warm others it would just turn over without firing.
The cause was the cam sensor. The original fit is a cam sensor with wiring harness attached. The wiring becomes faulty and as this sensor is only used during the start cycle that is most probably the cause of your problems. I assume, once started the car runs fine in all respects?
The new sensor and wire come as 2 separate parts. Change them, it is relatively cheap to do and hopefully this will solve your problem.
Jon, October 2008