maybe psu failing but see some tips below
check .
1. motherboard bios is update to latest and check the ram are working and are comaptible with cpu and mobo .
2. your monitor is new one.
3. you are using only the digital ports for display.
if you have a very old monitor () then you might have to buy a new one or use a active display adapter(such as vga to dvi-d/hdmi OUT).
most probably bios update should fix the no signal problem.
Also you may have to wait for a while for the display to come after that