As Aric mentioned though, this is unfortunately the result of an internal hardware failure.
This issue could be a manufacturing defect, but is also often caused by a power event (shock/surge, prolonged over/under voltage condition, etc).
This is something that would require repairs to correct; if you're thinking about a do it yourself repair, you'll need to be comfortable and skilled with electronics repairs, which could include dismantling the set (removing the back panel of the tv), diagnostics testing with a multimeter, changing out boards as needed, and possibly desoldering/removing and soldering/replacing individual components.
If you’re considering repair at a local shop, you’ll find a typical repair to be around $300 for diagnostics, parts, and labor.
Even though the tv is not very old, replacement will still make more sense. You can get a brand new LED tv with a fresh warranty in the $400 range.
Of course you could also call and complain to panasonic - while the warranty is up and they have no obligation to do so, they may be willing to help you with this since it is just past the warranty, or to give you some discount toward a replacement.
Depending how you’d like to proceed here, I can help with finding parts, finding a repair shop, or recommending replacement options. Just let me know.
Best regards, ***** ***** for the news,