Off/on startup problems Panasonic TX-32LXD70?

We have had the television from new. Visual performance, as Which? magazine rightly listed was outstanding. About six months ago a 'problem' begun. We start and finish our viewing with the power button on the set - rarely put to stand-by. Now on startup the tv reverts to a flashing red light after about eight seconds, sometimes after a milisecond of connection - and of sound only.
Turning off with on/off set button then Restarting solves the problem and we have normal, if delayed, operations. Any ideas why?