Players using the Oculus Rift are prone to having extreme viewpoint jitter every time the framerate drops below 45fps (like your shaking your head up and down very rapidly).
The issue isn't tracking as the SteamVR overlay isn't affected and the "mirrored" view on the desktop (the rift shows what your seeing in a window) doesn't show the same problem (it's perfectly smooth).
Using brute force methods like overclocking (mainly CPU) will help as they raise the minimum FPS but thats not tackling the root cause of the issue.
Disabling AWS in both SteamVR and Oculus Home yields an improvement but doesn't eradicate it completely, I suspect these setting simply amplify the existing issue.
Its very frustrating seeing the mirrored display (in 2d) looking perfect but the VR dancing all over the place, can you look into it?
Edit: I've found a visual example on YouTube (https://www.youtube.com/watch?v=LECu9tB_HOA).
In this case it's a Vive having issues with a Oculus build of unity but the the distortion is identical.