This happens to me all the time in sports. Table tennis, soccer, juggling, Frisbee, etc - I start playing and everything just “clicks” and I don’t notice any balance issues. But standing in one place drives me nuts, or walking slowly and stepping slowly, or geting in and out of a car. I think when the body is in lots of motion (such as sports), the eyes and proprioception takes over and the vestibular is not really handling much, at least that’s my theory for me. When I start to move slow, proprioception has trouble, so then it falls mostly to the eyes and vestibular.
Interesting it happened to you in golf though, that has a lot of walking. But a fair amount of proprioception and eyes during the swings, so maybe your brain suddenly flipped more towards the eyes and proprioception for a bit and didn’t pay much attention to the vestibular. In addition, you are in wide open and flat spaces, where the eyes are not giving you as much information about precise location as you move, so there is less mismatch between eyes and vestibular systems. I also do much better in wide open and flat spaces.
I too find that after sleeping all bets are off again. Things change in my brain and then I need to recalibrate all the sensor systems. Or, maybe the sensor systems are changing and then I need to recalibrate the brain, hard to know. Either way each day is like the movie Groundhog Day… except there is small progress month over month.
Super interesting observations, lots of room for interpreting what is going on! I often wonder if I just play Frisbee all day would I get better faster? I don’t think so, but maybe I should try (-: