I wondered this the first time going to a temple or shrine in Japan. It’s also quite common here. I wondered if maybe it came over with Buddhism and it made it’s way into the now-mostly-unified Shinto practice (pre-meiji-restoration, beliefs and practices were a lot more local). It could also have come in at the time of christian missionaries, but that seems a lot less like especially since it persists after the christians were forced to leave, convert, or die (though hidden christians remained, often meeting in caves in the hills and such).
I think one would have to search through what written accounts of people remain, particularly those of outside observers in a new place.
I thought maybe it came from some older homo sapiens practice, but even things such as nodding for yes aren’t consistent, so maybe not.
Also, if at all possible, wake up and go to bed at the same time every day including weekends.
This works for me when in the system. The only bad part is if I’m on call or on holiday, my schedule easily gets smashed and takes a long time to get back (some people are luckier and can adjust instantly). Edit: Also, try to make sure you ARE getting light during the waking hours, preferably natural light; this helps with your body’s natural rhythms.
Edit2: also, try to move. Being fully sedentary is hard mode. Also lol at the downvote. At least say why. I realize not everyone is able to do all those, if that’s what your after, but this has all helped me.