It started yesterday morning, but it wouldn't start in the evening. Tried again today and the same thing. When I try to start it, it turns over and sometimes it will start to fire but as soon as I release the key it dies. Pretty confident it's not the battery, I've tried jumping it with two different cars. It has been getting colder here (yesterday morning had ice on the windshield for the first time) so I'm thinking that has something to do with it. Any advice on where to proceed from here would be appreciated. The car is German spec if that makes a difference.

 

I have the same car and had that problem earlier in the summer. The difference being mine did not wantto start after it was warmed up.
I was advised that it could be the coolant temp sensor and yup, that was the critter!
BENG