Why does my iPad have a symmetrical whit fog on the screen?

So my iPad randomly flickered then the screen turned white and foggy, the border of the screen is perfect no fog. The iPad hasn’t been dropped or wet and works fine but still got a haze on the screen.

It happened a few weeks ago and I checked it today and it turned oneiththe screen back to normal, but 10 minutes into typing it flickered and turned foggy again. Can someone help please!!