Hi @cacornett58 ,
What is the model number of the TV?
The standby power light coming and going indicates a loose connection or a poor connection (dry solder joint?) that may be affected by temperature perhaps i.e. cold contracts- no connection, heat expands - good connection. It doesn't take too much to make for a poor connection.
The low voltage signal from the power board to the mainboard that power is available so the standby LED would be on, could be disrupted as the voltage (5 -11V DC) can't as easily overcome the possibly higher resistance connection as would 120V AC.
You may have to check if there is a service manual available online for your TV and hopefully that is has a schematic of the power board so that you can initially trace back the standby power circuit.
Just search for ''Panasonic (insert full model number) service manual'' to hopefully find results