Okay, I have a custom computer so I don't really have tech support on it. I either need to fix it myself or ask a forum what's what.
This issue seems to have resolved itself, but I believe this is the second time this has happened and I'm wondering what's causing it. I turned my computer on and it went through a fairly standard power-up (fans came on, LEDs, temperature gauges) but right at the point where the monitor would normally come on with the mobo splash, it completely turned off. It stayed off for about about five seconds and then it repeated the process. I cycled the rocker switch on the PSU and turned the computer on again and the same thing happened. I threw the rocker, unplugged the power from the PSU, plugged it back in and then turned the rocker. When I hit the power button, it went through a slightly sluggish but normal power-up and it's working now.
The computer has done this once before but it resolved itself after one or two cycles. I think it went through three-four cycles this time with no resolve. My only hunch would be a PSU on its way out, but this is probably wildly off. Any thoughts?