Yes - just to confirm that last post. Don’t panic. This reset will almost certainly work. Once you’ve held the ‘Power’ and ‘Home’ down for 30 seconds (it feels much longer because your heart is pounding so hard) the White Apple logo will appear and the reboot will start.
Don’t panic - no files or apps will be lost. The reboot takes quite a time so, depending on the time of day, make yourself a coffee or pour yourself a generous glass of wine.
It’s heart-stopping, but don’t panic!!!!
You’ll soon be up and running again. There doesn’t seem to be any consensus as to why this happens - just ‘one of those things’ as they say.
Good Luck!
Tim
Scotland