Start up problem with the 05 design??

[truoca]

Hi all, I need some help or advice please.

3 weeks ago I picked up my new astra 1.6 design, 80,100 miles. When we picked it up everything was fine, looked under the engine and everything look as clean as a whistle, since then I've had a few problems...

- on the second morning it wouldn't start up for about 5 minutes :/ turn the key, ticking over then dies but doesn't fire up???
- 4th day get to a roundabout after work, I'm in first gear, then the engine drops to 200rpm then stalls and engine light comes on. I turn the car off then on again, it starts up fine and engine light has gone???
- 3 days ago, after work on a hot day sat in the car park and it wouldn't start up, with the same problems as the first time???

But every other time apart from these 3 individual circumstances it starts up perfectly fine :/

Since then I have had the battery checked and that's all fine. As we have warranty I called the car sales and they said take it to the garage they use. Took it there where it spent a few hours, when it comes to picking it up they say they can't find any problem with it.

Please help??? Thank you