I'm getting this really irritating effect on my DK and I've seen this on my NB too. I' like a confirmation if anyone else also gets this.
Basically when I use "unrelenting grip" on my DK I get a 30% speed boost for 2 seconds. Only problem is the white trails effects becomes permanent!!! Its random, but I get this at least before I get to my 2nd or 3rd fight after logging in. The effect stays permanent until you get a decent loading screen, like entering a delve or using a far away wayshrine.
If I wanted a tail I would have rolled an Argonian.