Power button not responding and screen freezes on pressing reset

Hi!

The power button of my Tablet is not responding(it can't on or off the device) i try starting it up by pressing the reset button, it came up. So, for me to proceed and unlock, it will then freeze and after few seconds the screen will go to sleep. The charger is working perfectly and even when the tablet is on battery the same problem occurred. What can I do to solve this problem?