Ever since installing Dawnguard, Every so often (Actually more frequently as of recent), Ill be walking and my characters movement speed will stutter/stop.

Anybody else run into this/know a fix?

I've run into problems like this before in oblivion and in most cases it was something in the world bugging out like a dead body clipping in and out of the ground really fast. Either move the body or item or if you can't find it use the wait option for a few days. If this dosent help then I'm sorry I don't know what the problem is.