Sudden appearance of a scope-like overlay

A recurring bug causes a scope-like overlay to appear during gameplay, with black edges and a blurred screen. It disappears after a few seconds but keeps coming back, seriously disrupting normal gameplay.

As you can see, the screenshot shows black edges around the screen, creating a scope-like effect even though I am not aiming. It provides no benefit at all, and the image becomes very blurry, which interferes with my controls and aiming. This bug appears for a few seconds for no reason, then disappears, only to show up again after a few seconds. It keeps repeating and is extremely frustrating.