coloured horizontal & vertical lines ghosting on Samsung 49" TV screen

Hello,

I have a 4 year old Samsung 49” TV. For the past 3 weeks it has started showing horizontal & vertical lines, that appear sometimes for a few minutes sometimes for about 30 minutes & then disappear on their own. i’ve changed all hdmi cables as these are the only ones connected & it is still the same.

If anyone can help, it would be appreciated.

thanks,

Richard M.