I have a Magnavox MS 3652 S237

I have read alot of topics similar but have not seen one that quite fits my issue.

My TV turns off automaticly. When it does this, the power light stays lit. Once I turn it off and back on, it will stay on for a certain amount of time and turn off again. Whenever this happens, sometimes it will stay on for a hour or so and other times 2 minutes, 10 minute, etc.

Here's the kicker. When the cable is disconnected, it will stay on til I turn it off and does not shut off by itself.

Any ideas?