Hello ive been having an issue ,built pc a year ago and all was fine until recently i power on pc and all lights fan, everything comes on but keyboard and screen stay black after a few hours they will come on and finally display my log on screen then all is great till i restart it and does the same thing. My motherboard will roll through a few codes and stop on 4f and keep doing this till after a few hours shows log on screen. Any suggestions would be greatly appreciated thanks!