iPhone does not turn on

At a sudden, my iphone is turned off by itself and after 5 minutes start vibrating endlessly...

I tried everything to turn it on but I failed. I tried to hold the home and the power key together but it did not work. I tried to recharge it, restore it by itunes, itunes does not recognize it at all, and even took it to a local repair shops but they couldn't fix it.

Now it stopped vibrating and after I recharged, it does not vibrate...

Could you please help me