Computer issues

[Evanbaseball9]

I built my pc about a year ago and it was working fine until recently you’ll just be sitting at the home screen doing noting and the monitor will go black like the computer has fallen asleep but when you move the mouse and hit keys on the keyboard it does nothing all the lights and fans are still spinning and when you hold down the power button to force restart it does absolutely nothing you have to manually turn off the switch on the power supply then restart and it keeps doing it but I don’t know what the issue is. If someone could please help that would be awesome 

[ChaoticChaosx]

Could be RAM, display cables, (HDMI, DP, DVI) GPU display ports or GPU itself.

Need to run memtest86 and/or try one by one at see if they show up in bios first.