Panasonic TX-P50ST50Y keeps switching itself off whilst playing files from my hard drive

[Mactabanoye]

Hi, I have a Panasonic TX-P50ST50Y which I bought back in 2012. I have never had any problems playing MKV or MP4 files from my Hard drive into the USB. For some reason the TV has all of a sudden started to switch itself off and back on again. It did it yesterday but I switched the usb slots and it worked fine. I tried that again today after the problem returned but the TV is not having any of it.

I have checked for a system update but it has the latest firmware. I have reset to factory default. I have switched off eco and power saving functionalities but the problem persists. Please, can anybody point me in the right direction to resolve the issue?

Thanks