Question Odd wavy lines behind the screen.

[vpiscitelli]

I have a Dell 32 Gaming Monitor G3223D monitor. Recently I have been seeing these wavy lines behind the screen. It is definitely not dirt or staining. It is stationary when I scroll. It is most evident when looking at darkish colours.

Any idea what it could be??

https://imgur.com/E4fYdpd

 

[Lutfij]

Any idea what it could be??
You've posted just one image close up. Can you pass on an image of the entire screen? Do the wavy lines go away with regards to time/usage as the panel is kept powered up and running?