Hard to turn on

I bought this Plasma TV from Sears as is with the right lower corner plastic bezel broken.It came on in the store ok but lately the TV wont start after it sets in the off position for a few hours.To get it to come on I have to hold the power button down until the TV clicks in the back.Then it works normally to come on and plays beautifully.Sometimes I have to hold the power button down 2 or 3 times to get it to stay on.