Usuall in most cases its the PSU, graphics card can do it to but by simply taking it out and starting you should know if thats the hardware malfunctioning. It sounds like a faulty power supply to me, only use good name brand power supplys to avoid this from happening, I suggest coolermaster, antec or corsair.
this can happen without there having to be a hardware problem. I have had several boards do this over the years and resetting the BIOS usually takes care of it. It can also happen if the board was improperly installed and something shifted causing a short.
It could of course be a failure, or power surge. i have had one board do this because of faulty capacitors
I got the new MSi z77a-g45 mobo. I installed it 2 weeks ago. I never moved it an inch. It was working every day until this morning. I looked at all the standoffs and there isnt one out of place. All the screws were carefully screwed in. So that leaves RAM, CPU, and HDD. My RAM looks pretty cheap. My CPU is an intel core i7 2700k. My HDD is a Seagate Barracuda.12 1 TB hdd. Can any of these cause problems?
if you tried to over clock your new rig the over clock cold have failed. if it did the mb could go into a reboot loop. have you tried clearing the cmos and seeing if the mb will post??? most times if i get an issue like that that you can pin point..(no burn marks or borked parts. try to barebone the build. unplug power to the hard drive and or sata cables..unplug the keyboard..mouse and any cards. pull out all the ram but one stick and the video card...see if it stops rebooting. if it does plug the keyboard in firs..then mouse and see if you can go into the bios and reset it and then reboot and see if the mb is fine. if you have a friend that has a muilti meter you can put your ps on a table and green wire it. (jumper it so that it comes on without a mb). and check the voltage outputs.