This is something I've encountered a few times, but it's related to spawning. If I'm running and holding down one of my directional keys and I get killed, when I spawn, sometimes it acts like I'm still holding down that button and my character will move in that direction. I have to tap the key to "clear" it. Sometimes this has happened with the shift button that I use for running as well, where I can't run until I tap the shift button a couple times. There have been times when I've spawned and immediately done a combat roll.