I'm level 4, I haven't done anything... literally. I did one sidequest to get a key from a guy (bad guy) and I'm back at the first town. I go into a store, sell some stuff, come out, and three guys are there and say "We're here to teach you a lesson!" then proceed to whoop my A**. I mean, I have to hit them around 40 times to kill them... and there's three of them that kill me in four hits. I can not beat them, I can not run away... when I die it just respawns me there and they kill me again and again and again... what's going on? WHAT DID I DO.

a unfortunate situation... probably should try to lure them in to a building and sprint for the door when they are in the back or simply start over from on of the autosaves or even just start over... your only lvl 4 wont be to hard to catch up

This happened to me as well and appears to be part of the game, not a glitch.

I was able to beat them by running into the water and drawing my bow. They split up when I did that and I was able to engage them one at a time.

Try luring them out into the water and see of that helps.

same thing happening to me at level 7 outside of White Run. 4 thugs, one guy can kill me in 2 hits. Tried running, bow and arrow, etc etc. I figured I would have better luck if I had a follower (and I had just recently earned one but didn't invite them along).

Definitely seems to be part of a storyline as they say "That's the last of them" when I die as well as "That's what you get for taking things that aren't yours."