I am experiencing often freezing problems after updated iOS 15.1

I had similar problems to what you describe. The cause was that my iCloud was filled to the (5Gbyte) limit - which didn’t seem to cause problems until the iOS 15.1.1 update. Then it was shockingly unreliable - most apps including just “settings” and the App Store would freeze regardless of updates and work for a while after powering phone off and on; but would freeze again. Check your iCloud capacity and either upgrade or free-up space if it says it’s full.

Please follow the steps in the following link for support with this issue: If your iOS device restarts or displays the Apple logo or a spinning gear unexpectedly