Your motherboard is failing its power-on self test (POST). That means that it's checking for all the connections to work and when one doesn't, it powers off, then tries again. This can be caused by multiple issues but if you have the time, you'll certainly find what it was.   The first thing to try is to clear the CMOS on your motherboard. Take the circle-shaped battery found somewhere around the CPU socket and remove it. Keep it off for a minute before putting it back in. With some lu