I'm currently playing a character at LV65 (Dunmer Mage/Archer + Vampire Lord), and I'm experiencing this weird phenomena of being attacked by NPCs like..."Orc". "Argonian". "Imperial". They have decent armor, but no loot aside from maybe a lockpick, and they show up on both Skyrim and Solstheim to randomly attack me while I'm traveling as if they're bandits. They're always by themselves, and are always hostile when they show up. I have no mods that have anything to do with enemies or NPCs (unless a mod to marry Teldryn somehow makes this happen).

What is this?

There is a random encounter that has an NPC, only named by their race, attack the player.

Edit:

http://elderscrolls.wikia.com/wiki/Random_Encounters_(Skyrim) calls it "Hostile Traveler".

Its normal. When I travel long distances on foot, like Windhelm to Solitude or Falkreath, I encounter them.

And it's a very common encounter,at least it is for me.

Normal. They sometimes have skooma in their inventory. There is even one location I can think of that has this type of random encounter spawn. The south easternmost road out of Skyrim (down below and beside Riften) spawns a hostile, horse riding "race."

I only find them hostile if you attacked one of them, or fought over a skooma deal. Otherwise those guys just normally walk past me and I can buy skooma from them.

Sure you're not confusing the skooma dealers for what the OP is running into? They are two separate types of encounters.

The ones the OP is talking about are, well, you might consider them newbie bandits who haven't earned the title yet. Kinda like petty crooks v.s. gang members.

When I encounter these guys, they're typically running at my character with a drawn weapon, already hostile. They're not the roadside dealers.