I can't tell if it's the power supply or if something is loose.
When I started my computer from hibernation it turned on, then off, then on, then off until I readjusted the power cable.
Another time I turn on the computer to find the monitor doesn't turn on. I turned off the computer then on again and the monitor started to work.
This graphics card says it needs 400w minimum and my computer has a 460w power supply.