With new cars, the mechanics can plug it into their diagnostic computer and tell you exactly whats wrong. It could be any number of things.
>> will only start for few seconds then die when I unplug the battery cable, then plug it back it.
So quit unplugging the battery!
One thing that comes to mind for me is what happened to my sunbird was that it didnt want to start. It would start, and then sputter for a few seconds, then die. It was the O2 sensor that was shot. It couldnt detect the levels of O2 in the exhaust, so it kept flooding the engine. It was a $30 part to have replaced.