Many Iphone features freeze or don't work entirely.

My phone is on IOS 18 and has begun to function improperly. What started out as a small problem of crashing on an application, the Chase app, to being unable to install it after (left on an eternal "loading" sign), to the phone completely freezing up when I even try to factory reset it or sign out of my Apple ID. I've tried every possible solution I can think of. Storage is good. Wifi is good. The battery is good. No visible damage to the phone. What could possibly be the root of this problem?