https://wccftech.com/several-pixel-3-units-plagued-with-shaky-cameras/

The Pixel series of devices have long been praised for their impeccable cameras. The cameras work well, in part, due to the Google Camera app, which is powered by the company’s secret sauce. But not all is well in the Pixel 3 camera universe, as several reports have emerged in the recent past about it shaking/stuttering/vibrating. Google’s product forums are littered with hundreds of threads, and there seems to be no solution in sight. Here’s a video of the instability in action:

As seen above, the viewfinder in the Pixel 3’s camera app shakes a lot, resulting in jittery photos and videos. Considering that the problem has been around for months and not a single software update fixed it, the likelihood of it being a hardware problem is high. It could be that the camera’s autofocus or OIS (optical image stabilisation) mechanisms are broken. Some users even report an audible noise coming from the camera, reinforcing the notion that it is a hardware problem.