So, just started up a Dunmer Sorcerer and went to do the barrow quest, when all of a sudden i started getting attacked (and then killed) by something. there was a red dot on my radar, and i was clearly being attacked by something, but nothing was on my screen. After i respawned, it happened again a couple seconds later.
The kill screen said i was killed by a Skeleton Warrior, and i DID pass area's where they are normally standing, but with nothing there at the time. MY Familiar was also attacking something, but did not seem to do anything before it died.