Did you happen to build your computer on top of an ancient Indian burial ground?
Maybe he should turn it off... and back on...
But in all seriousness..
You could have a short with some of your wiring.
My advice would be to check all the wiring incl. the front panel connectors ( you may need to refer to the motherboard's user manual to find out which wire is for the power button)
It could be an issue with either the Power supply or the motherboard, make sure they are both properly seated and have no wires exposed.
If you still have a problem, completely disassemble the PC and re-build it. This way you will be able to thoroughly inspect each part for possible damage.
If you are still experiencing these problems and there appears to be no signs of a shortage from the cable or damage to any cable/hardware. A new Power supply might be in order.