I'm sorry to hear you're having problems with your television.
Normally in a case like this, if you can imagine your television being able to stay on for about 10 minutes, I'd suggest a firmware update found on the website for the television.
However, since you aren't able to maintain the "On" position, my best recommendation would be to call 800-SAMSUNG and have a service tech take a look at it.
This is a rare problem, but we can help you get it back in working order.
I purchased a Samsung A750 46 inch LCD in October and today when the TV was turned on it started cycling on and off without ever registering a picture. I cannot get it to stop. any suggestions?