iPhone8 11.1 Shuttering sometimes after unlock

Hey,

I have a new iPhone 8 64gb since 6 weeks and it has sometimes a little problem. After unlocking the phone with finger-id the iOS is shuttering and running like half of frames per second and its not anymore smooth like always.

I used a icloud backup to setup it.

Is this an iOS bug which will be fixed in the future?

Greetings!