Why Samsung S Duos, Switches of Automatically even when locked with Pin?

[sarahgad]

Hello everyone, this is Sarah. A friend of mine uses a Samsung Galaxy S Duos as a second phone.
Recently he has been facing the issue of the phone being powered off whenever he keeps it in his pocket.
The device is always locked with a pin-code, yet he has to turn it on every now and then because it switches of itself.

Please, if any one knows the solution to the problem kindly help

Regards
Sarah