I feel this.
On the verge of sleep, not a care in the world, and my brain pipes up with some horrifyingly embarrassing thing I did as a child that I suddenly realize I've just done again as an adult.
Next thing I know, hours have past as I ponder everything from social faux pas to the sound of tree frogs outside my window, the way my wife breathes... and then the fact that I'm suddenly aware of my own breathing.
"Everything and nothing" is state normal inside my head.

Oof... I felt this...

Described excellently.

Albeit, there's always the constant torment in my head at all times, but the silence and lack of distraction when trying to sleep only serve to give way and to amplify such dwellings that would otherwise be more or less drowned out with activities.

Those rare moments when I can "gamer trance" and get lost in a game to shut out the outside world and fill the silence between my ears are deeply cherished.

No existential dread. No wondering what happens after death. No lingering thoughts of "what if I just walk off down the freeway and see what happens?" No anxious silence. No echo chamber of stupid memes that have gotten stuck inside my brain.

Just a few minutes of blissful focus on the task at hand satisfies in a way that lets me pass out in short order.

After the adrenaline dump of storming Normandy's beaches, of course. lol

Having OCD in a nutshell: