It' dangerous high voltage, and you need special tools. The TV stores voltage charge after it is unplugged from the power.
You should either have an experienced person work on it, or buy another TV. Costco has deals.
If your going to open it up then firstly know what ur doing. Second hold the power button on for about a minute to discharge all electicity that has been stored. And third make sure you know how to put it together again. And go from the easiest problem to fix down to the bottom of your list. You dont wanna try anything too extreme if you don't have to.
Is this an LCD? There are quite a few out there that have this symptom due to bad capacitors on the power supply. Think about your level of comfort working on these circuit boards, and decide if you should call a servicer.