I wish I had a solution, but I don't. It may be that your power supply needs to be replaced, but outside of being able to actually look at it, I'm really unable to give a thorough diagnosis.
My Samsung is steadily taking longer and longer to turn on. When I try to turn on tv after it has been not used like overnight it takes it 5 minutes or longer to power up and keeps on clicking before it will turn on. Sometimes it wil not turn on. It's been frustrating to say the least. Once it is "warm" it will turn off and on ok. Once it turns on it works fine. Tv is 2.5 years old. Any suggestions would be appreciated here. Thanks Jack