I get this too, OP!
On a train, I sat in what was an unreserved seat for part of my journey which then became reserved further up the line IYSWIM. The people arrived whose seat it was (a mother and late teenage daughter), the mother said ‘that’s our seat’ so I gathered my stuff to move, and as I did so, the daughter glared at me and said ‘you’re not getting it’ 😵💫 I was picking my things up at the time so clearly not planning to fight them for it! 🤷🏻♀️
Also had a weird encounter with a man from the council delivering our new recycling boxes a few weeks ago. He dropped off two identical sets, so I said we’d only need one, as we don’t have storage space or generate enough recycling. He asked which set I’d like to keep, so I said (completely genuinely), ‘well, they’re both the same, aren’t they?’ To which he replied ‘well that’s put me in my place!’ 😮 I was shocked that he’d inferred I was being rude to him or putting him in his place, when I was genuinely looking at these identical recycling boxes.
I’m also a young-ish woman, early 30s, quite quiet which could be construed as meek, always (try to be!) unfailingly polite. So maybe it is that that rubs people up the wrong way, or makes them think they can take their stresses out on you, like PPs have said.
I’ve also been out walking my dog on the way to the vet, and she stopped to do her business, I had bag in hand at the ready (luminous green, so not exactly hard to see), and a passer-by said ‘there’s countryside up there, you know’, admonishing me for letting my dog do her business on the way to the vet 🤷🏻♀️ it’s not as though you can ask them to hold it!
Sorry you get this too, OP, it really baffles me.