To shut the phone down I hold the power button until the options to Power Off, Restart or Screenshot appear. Selecting Power Off merely restarts my phone. I initially thought I had absent mindedly hit the wrong option but I’ve been through it multiple times and it looks to have gone off and in about 30 seconds it restarts.
The screen is in pristine condition so I don’t think it’s anything related to that. It’s very frustrating as I have a phone I can literally not turn off!
Any thoughts appreciated.