There is a green flashing Timer light con...

There is a green flashing Timer light continually flashing on the tv which disables the TV from being turned on. This light randomly goes on without warning and until it clears the TV will not power on. I have been unable to get this timer light to de activate over the last 2 days even though I have unpluged the tv repeatedly. This proble has been a re-occuring issue for the last 2-3 years, but never has it remained on for this period of time. How do you clear this timer light and what is causing it to activate? The TV is a 52" w/ a lamp light and apprx 4 years old.