Recently my PC (which is running Windows 10) has started switching itself off after a short time of not being used (ie, an hour or so). Or perhaps I should say that the PC seems to be still running but the screen is just blank.

All I can do is switch it off, but then when I switch it back on again the screen just stays blank. I'm having to keep switching it off with the power button and then back on again. After several attempts it will boot up but it seems to be totally random.