I had this issue for a while, did not manage to reach any help from Sketup support.
Big Sur 11.1
Processor 2.7 GHz Quad-core Intel Core i7
Graphics Radeon Pro 455 2 GB
Sketchup Pro 21.0.392
Problem: The navigation is very slow, it keeps freezing, the loading wheel on the mouse pops up every few minutes and It’s almost impossible to work with more complex components.
I reinstalled my entire laptop, updated the OS and it feels like it’s even worse than it was before.