Have you tried to unplug your TV for 5 mins? Also, have you tried changing the batteries in your remote?
I have 3 Samsung Tv's which have each also started doing the same today. I've unplugged and reset them. Removed all accessories (Chromecast, firestick, Now TV s. There's no available update for any of the TV'S. I've reset my router and disconnected the Tv's from the internet all to no avail. Just pleased someone else has same issue. Its not remotes or power supply issues. Obviously some sort of software issue.