It seems when the character exceeds a threshold on either of the left and right sides of the region, the camera follows as if it's towed by a very short string and it has a hard time keeping up with the character. Almost like it's accelerating, but then stopping in very short spurts. Theoretically, that's what's causing the jitter effect.
I think centering it to the character is a good start and might do enough. But there are ways to smooth out that transition to make it less jarring, sadly I don't have solution to just throw at you, so you you might have to lurk some guides for that.
Best of luck!