iPhone 5 turns off and keeps needing restore

my iPhone 5 needs to have a full restore done every few days

it will turn off on its own sometimes for a few times I get it back ok but it soon won't come on at all and then needs to be fully restored and then have the back up done

when it turns off the screen sometimes goes into lines of various vertical and or horizontal lines and different colours

faulty graphics chip maybe but it seems to corrupt the operating system on the memory chips ?

Any help would be much appreciated