Sometimes during a car ride when I'm in the passenger seat, tired, and there's no conversation going on, I close my eyes and let my thoughts wander.
I also tend to focus on sounds, things I feel and also whether I can recognize where we are approximately by the car's movement and the lighting through my closed eyes. It's kind of a habit I've taken with me from experimenting with some meditation that I still do when just relaxing for a bit.
Occasionally, I drift off to imaging some stuff, like continuing a conversation or a scene of a story I just thought about, taking a walk somewhere or other simple things like that.
I'm still aware of everything else around me, just that my focus is more on my imagination process. Usually I also ponder when to open my eyes again to check whether my location estimation is correct.
Just recently, I was imagining a conversation between two people, one advising the other on some matter they had a discussion about. I kinda slipped more into the role of the "teacher", while still also thinking about how the "student" would react.
The scene was sort of visible, yet not like a true dream.
At the same time, I noticed a shadow passing over us (the car), and thought to myself "oh, so we just passed the bridge", while continuing the internal conversation.
A bit later, after some turns, I wanted to confirm if my guess about our location was correct and opened my eyes in the middle of the conversation.
My guess was correct, and I tried to remember what I just thought of, as it seemed like I was at the verge of falling asleep. All details I just had in my mind a moment before were gone. All I could remember was that one person explained something to another, and that just barely.
Any content of the conversation I just held has vanished, no idea about the topic, what relationship the people had, how old they were or what they looked like.
That's the usual thing that happens, though I rarely remember anything at all other than it was kinda fun and that I'd like to continue, but can't.
A "deeper" kind of daydreaming