If I understand what you mean, I might have experienced something like it. I think I noticed it more when I was a kid, especially while sitting in my desk at school when I’m done with work, any time I could daydream a bit. It’s a nice connected feeling to my surroundings, almost feeling like the world is alive but not really.
That’s how I interpret this poem When Traveling I Used to See - someone who felt this kind of feeling and experiences/daydreams it as girls watching him. I take it like anthropomorphized version of the feeling you describe.
I suppose it’s some kind of mild meditative state, and probably also related to your body being relaxed in general.
Or, alternate theory, maybe you’re just animalmaxxing. I mean, you ever look at a goat or something and think how they’re so content to just stand there and do fucking nothing for hours? Maybe it feels really damn good to do that for goats. Humans are animals too, maybe you just got to that part of the brain.
To be honest, the animalmaxxing theory was just to amuse myself, it’s not a real thing as far as I know. But you ever look at a cat just staring at a wall and think, how is the cat not bored?! It must be because it feels good