AGAIN AND AGAIN MY MACBOOK IS ON AND OFF, AGAIN AND AGAIN MY MACBOOK IS ON AND OFF

1. Please don't do the all caps thing. It's regarded as rude, like yelling, and it's harder to read.
2. Hold down the power button until your mac shuts down.
3. Hold down command and R and boot into your recovery partition
4. Repair your hard drive and permissions with Disk Utility When to Run First Aid in Mountain Lion's Disk Utility - For Dummies
5. See if that helps.

If you are getting a kernel panic, try starting up in Safe Mode by holding down the shift key on restart.

http://support.apple.com/kb/ht1455

If it boots into safe mode, you have some incompatible third-party software.