When I am playing I prefer to sheathe my weapon when not in combat especially in towns yet the following things cause it to become unsheathed:

1. the random friendly spell casts have around a estimated 20% chance to force-draw my weapon (that's right I am talking to you people who spam the speed spell)
2. when someone nearby decides to pick a fight It may happen (rare)
3. no reason at all. (also may force-switch my weapon instead or in addition to drawing) (did not recall seeing this one as often until after 15)

Is this happening to anyone else at all? It is happening to me a lot and I must say it is getting really old really fast. and before you say anything i was once force unsheathed by reason number 1 in the pause menu before LV 15 so there was no way I "accidentally hit the <- button or the triangle button" as those would not have done a thing then.