Continued attempts can result in higher repair bills. Call it in and get an estimate.
http://answers.us.samsung.com/answers/7463/product/LN52A650A1F/samsung-ln52a650a1f-questions-answers/questions.htm is interesting but since this is not a repair forum I think it best this TV is unplugged as soon as possible.
Why I find that link interesting is the BAD CAPS statement and that the LN**A is listed at http://www.samsung.com/us/capacitorsettlement/ but your device model is just a little off the list. I'd still call it in and mention BAD CAPS?
I have a Model # LN52A650A1F from Samsung that started making a loud noise, shuts it's self down and restarts. Any ideas?