I've experienced this my entire life. As a toddler, little kid, I do seem to recall a lack of thinking. Specifically, I remember adults waving their hands in front of my face to get my attention. As an adult, I've learned how to function through them.
My therapist used to catch me falling into a staring spell in the middle of talking. I can reach for my drink and take a sip off of it while this is happening. I've been accused of daydreaming, spacing off or not paying attention when it does happen, which is far from the truth.
What happens to me is as a kid it was just like you described everything goes out of focus and my thinking becomes more relaxed. As an adult, I don't lose focus anymore, but my eyes lock onto whatever it is that I am looking at and I struggle to change what I am looking at. My thinking does not change now either, as I said, it happens to me while in the middle of a conversation and most people can't see it.
The anxiety medication I take causes these spells to happen much more frequently, so maybe this is something you could look into. Being tired or lack of visual stimulation are my main two triggers.