HELP!!! Mac turns on and off repeatedly. .

I bought a macbook pro used in 2013, I believe it is a 2010 model. I was trying to reinstall OS X and package to the labtop to clear everything on the drive. It started to restart then failed and turned off with the motor still running. Then it would repeat that process start up seconds later to a grey screen and the rebute sound then seconds turn off, seconds later turn on then back off. This went on for 1 hour. I tried to eject the disc but I can't do anything except watch it turn off and on until it dies. Any suggestions to help me fix??