cursor hovering and walking

I've combed through almost every mod I own, but I can't seem to figure out what is causing this issue... When I hover over an object with my cursor, the action seems to shake on and off, as though I'm not quite hovering over the object, making it difficult to examine or take actions on the hovered object... similarly, when walking, I can't hold the mouse to change direction, I have to click somewhere new to change directions. This is happening with pretty much all the mods, but not on other servers with fewer mods and less resources.