imac screen showing temporary tint

hello, my imac screen has now twice had an issue where i've had a blurry mark that forms (in an unknown span of time but i guess less than a minute cos i didn't even notice it coming on) and then disappears after about 30 mins. Wondering if anyone might know

a) why does this happen

b) is there a repair for this

I'm beginning to wonder if its a warning sign that my screen might have some issues coming up in the near future.

Video to view the issue - https://youtu.be/qbHJFv_489I