general problems of the 2009 Volkswagen GTI

I bought this vw Gti 2009 in 01/2009. Since last summer, the engine start to have issues when trying to turn it on. Here is what happens: when the engine temperature is cool, it has no problem to turn it on. But when the engine is already warmed up (e. G. , after drive 15 min on the freeway), and you turn it off. Then there is >50% chance it won't get started when you try to turn it on again. If this happens, I might have to try a couple of times then it can get the engine started. I have been to two different vw dealers for several times, neither can identify what's the root cause. In my last visit, I showed them how to reproduce the problem, and I left the car for a couple of days. But they told me that they cannot reproduce the problem.