I have encountered this with two characters now, and know of others who have as well. My character is walking along the road minding her own business, and passes a Stormcloak patrol coming from the other direction. One 'Cloak, who always seems to be female, draws her weapon and says to scram. You can walk by her and the others without trouble. But if you stand there, eventually she and the others go fully hostile and attack.

I am trying to figure out why. Both of my characters who have experienced this did not do any of the civil war, and are not members of the Imperial Legion. I think one character had a bounty, but it seems odd that Stormcloaks I meet in Whiterun Hold would threaten me about a bounty I incurred in The Reach (where said bounty was incurred killing Thalmor). My most recent character also had just finished the Saadia/Kematu quest, on Saadia's side. But I am not sure how that would make the Stormies go aggro. She is a new character, and has not really done much at all in the world. A few quests out of Markarth, and a few out of Whiterun.

Anyone else have this happen, and figure out what was causing it?

Are you any race other than a Nord? Some Stormcloaks are very xenophobic and this could be a scripted reaction to "outsiders".

One character was a Redguard and the other a Dunmer. However, my Wood Elf, High Elf, Khajiit, Argonian, Breton, and Imperial characters never had this happen. Not even the ones who were members of the Legion.

I have encountered this behavior from random patrols on both sides, SC and Imperial, before joining one side or the other. If I am neutral in the war and do not keep my distance or "move along" and let them go about their business unhindered when we cross paths, they will warn me off and can become hostile if I don't comply.

Edit: and this is on Nord characters, so it's not racially motivated on the SCs side.

I've had it happen a lot on my files. especially with my female Breton archer for some reason. One of many many reason I don't like them.

Interesting to learn it happens with the Impies too. My characters usually either attack them on sight, or give them a wide berth, so that is probably why I never noticed it with them. I just looked in the Wiki, and they have really upgraded their list of http://www.uesp.net/wiki/Skyrim:World_Interactions. They call them Imperial Scout Patrol/Stormcloak Scout Patrol, and differentiate both from the normal Imps/Cloaks.

yeah happened to my nord warrior other day.no civil war quest done yet.low level maybe 12 or something.had my bow out no warning they just attacked.i killed them.think im going to side with imperial this time anyways done nord last time.

I've always had that too and Empire soldiers or Thalmor patrols have the same behaviour. They will do this as long as you haven't picked up a side.

"Sons of Skyrim" my foot. My nord's killed more Thalmor than their entire army put together and somehow they still want to take me down for not taking sides. Imperial escorting prisoners aren't half as bad.

Arguable. Imperials with prisoners are just as bad as Stormcloaks on the roads. Yet, none are worse than the Thalmor. I talk to one, and then they start attacking me because they don't like how I look. I'm a f*cking Khajiit. The Khajiit are aligned with the Aldmeri Dominion (albeit being tricked by the Altmer by the disappearance of one of the moons). The Thalmor will attack anybody - ESPECIALLY if you are wearing an Amulet of Talos (but then again, I suppose that makes sense)

Same here, both Imps and 'Cloaks wanr me to stay away. Also, if I stumble into a camp. Not all camps though - the Whiterun Camp haven't cared neither about my Breton nor my Dunmer, but the Falkreath Camp is more alert.
I don't think the patrols on the roads have drawn their weapons, though, at least not the 'Cloaks, maybe the Imps a couple of times. Maybe I've walked away quickly enough.

My favorite was when I swam across the bay from Solitude, right under the arch, and then went up the hill to cross over the swamps into Hjaalmarch. I can hear/see what sounds like a scuffle up the hill a ways. Then an SC soldier comes down the hill, stops in front of me, and says something like "official business - move along" or whatever the standard warning is. So I moved away and kept walking, making a wider berth around the top of the hill than I'd originally intended, still wondering what I'd missed. Then the rest of his patrol catches up with him and they proceed on down the hill. I wait for them to get out of sight and run up to see what they'd been up to only to find the dead bodies of a Thalmor patrol scattered around.

If I'd been already aligned with the SCs I would've been welcome to join in the fight, but the way it happened it felt like the soldier was just warning a civilian away from a dangerous situation.