Software or hardware problems or both?

Regarding your point #3, read this and understand how control center works with iOS 11 or later:

Use Bluetooth and Wi-Fi in Control Center with iOS 11 - Apple Support

Then, in addition to what you've been told by Brian, I would say that:

Before restoring from your previous backup, I would check your points #1 and #2. If they are solved than your hardware could be without problem.

Shouldn't be this case, your iPhone needs to be inspected at the nearest Apple Store, and if you need this kind of service, please have your battery checked (point #4).

Regards

Giulio

Hi

Go to iCloud make sure iCloud back up is then backup now over your wifi

Then go to settings down to reset Restore back to factory settings.

Set back up over your wifi when it asks if you want to use iCloud backup Say yes to get your apps and data back this will get rid of any bugs.

Cheers

Brian 🇬-1F1E7;