Bro it is not iPhone issue. It appears the issues I faced is quite similar to the one reported here. I set up the phone as new and there was no data transfer done for the apps. I was using the iPhone 12 Pro and iPhone 12 Pro Max and replaced it multiple times. Both models were having issues.
Later I identified issue was due to a banking app which you least expect. You wont expect this to happen on a banking app. Once I uninstalled the App everything perfect. So in your case it might be one rogue app that is causing issues in the entire ecosystem
This is what I faced when the issue surfaces
1. Cannot download Apps from App Stores
2. Cannot send/receive new emails in the default IOS Mail App
3. Photos/videos cannot upload to iCloud but no issues with OneDrive
4. Settings get time to load occasionally
5. Navigate to Settings and choose any installed apps to view my specific app settings, the screen just freezes
6. While doing call with Apple Support at the time of issue, they won't be able to do a screen mirroring even though I allowed it when the option pops up in my phone
7. Based on my experiences it would start with any one App and affect some other apps. It could start with any random app either an inhouse IOS App or third party banking or social apps. Usually, it affects almost all the default IOS Apps and I won't be able to even connect to Software update Server for checks. The latest issue started when I made an attempt to download an App from App Store as mentioned in the point 1.The download failed from App store and after that issue started spreading to multiple apps. For example if I Went to the Gmail App and tried to Add another mail account. It hangs and don't allow me to add new email account. While facing this issue when I try to launch some Apps for example Facebook Citibank etc. (it could be any random app) it just freezes, and all the issues reported from point 1-6 starts popping up. At the same time some Apps work perfectly fine. I can watch videos in YouTube and all.
8. Once I reboot the phones all these issues get resolved and it would work fine for some days before the same happens again. This routine cycle has been going ever since I upgraded to the new series of iPhones. I don’t think it is Apple Hardware issue as I have replaced the phones thrice and all have similar issues.