Randomly when I'm playing the game will start to have a seizure and everything will jitter, I have no fps drops or notable changes in the advanced netgraph. But it feels like I have like 20-30 fps for a bit, and then it will smooth out. I've noticed this happens when I rocket jump sometimes, or on MGE/DM servers.
I have a decent graphics card (nvidia gtx 550 ti) and can hold 300 fps. I use the latest maxframes config.