Why does my iPhone’s wallpaper always change whenever I shut off or restart my iPhone

Hello there,

I recently just updated my iPhone 7 Plus to ios 11. In the following days I didn’t had a hard time using it. But just recently, my screen froze and I couldn’t touch the app icons or even scroll through my phone. But then I got it fixed from where I bought it, but whenever I shut off or restart my iPhone, the wallpaper always changes. Why is it like that and what should I do?

Thanks






I didn't find the right solution from the internet.
References:
http://apple.co/2g8DGGr

whiteboard animation