I have white criss cross lines on my screen when using camera - need to remove them

Until yesterday everything was normal !!!
I clicked or pressed something and now when I go to my camera, the screen has white lines going across and up and down, effectively making 9 sqyare.
The camera still works, but it is frustrating as they weren'tthere before, the screen was clear, and it is hard to view the subject clearly.

Any help gratefully received.

Thank you.