I built my PC 3 weeks ago and everything was working fine until last week. Now after i use my computer for a while and restart it, the monitor doesn't come on at all. Everything powers up and the gpu fans are spinning but monitor shows nothing and the hard drive accessing lights do not turn on. And when i hard restart the PC everything works fine and it boots normally. I tried changing the GPU slot but that didn't change anything. I know the problem cant be with the monitor because it works when i hard restart the system.
I saw this problem some time ago with another user but don't remember the exact fix for it. If I remember correctly the machine was going into sleep mode on a restart that triggered the display to turn off. It was some kind of incompatible settings between the BIOS and OS sleep settings.
Get into your BIOS and OS sleep settings and turn them off to see if that corrects the problem on restart. Then reserach those settings for your particular BIOS and OS if you want to re-enable the sleep mode.