Quick question,

I own A 2011 A4 and sometime when I turn it ON after being parked for a while, the car starts but it goes into a hesitation frenzy for a few seconds.

I don't know if its electrical or gas problem what causes this strange behavior. Any suggestions of what should I look for?

 

If you are still under warranty bring the car into the dealership. Even if they can't recreate the problem while it is in the shop they can at least run a few diagnostics. If you keep having the problem then continue to bring it into the dealership until a solution is found. It may require them keeping the car for several days but they should provide you with a loaner. Good luck!