Chiming in, I too experience that, so you're far from alone. I've been more aware of it lately. I have usually thought of it as an off day and cut the ride short. I do avoid riding on days when I'm tired.
I tried something the other day, and it worked really well. I had it, then lost it and decided to stop and get something to eat. I tried adjusting my focus as to what I wanted to pay more attention. Sort of a decision to hyper-focus on the riding and my lines while shutting everything else out. Also sort of like a shift from riding defensively to taking control and charging. (Something like a 'beats on chest' moment
) Anyway I was going to call it a day if it continued, but instead my best riding of the day was right after that. I was in a controlled environment at the time, so that made it less dangerous to take my attention off the surroundings and other riders/drivers. I was just really happy it worked and I had forced this old brain to get back in sync with the bike
I'll be trying a version of that the next time I seem to have lost my mojo
BTW I've gone from riding at 35psi to 42psi over the past couple weeks trying to decide what felt right. I settled on 40. Although at no point was I able to feel a difference in traction, it was just more sluggish to whip around at the lower pressures. I'm still tweaking, but I think suspension has more to do with that jittery, bike is trying to tell me it's about to loose it feeling. Which feels exactly like when I'm having an off day.
Glad you posted this, I was wondering if it was another sign of aging or time to stick to 4 wheels. Hopefully this means it's fairly normal and just something to be gauged like road conditions