I'm building my first system in about ten years, and having problems.
Gigabyte ga-p55a-ud3 MB
Intel I5 760
DDR3 1333 RAM, 2 sticks at 2Gb ea
Antec 500w power supply
After getting everthing installed I hit the power button, the LEDs come on, and fans start to spin, but amost instantly shut off. A few seconds later the system attempts to start again with the same result.
It sounds like your cpu is not getting enough power or it is overheating and shutting the system down.
1) Check your power connectors to make sure they are all connected, including the 4/8-pin CPU power lead.
2) Check your CPU heatsink to make sure it is properly secured to the cpu and the board, and the the fan connector is connected to the CPU_FAN