I have had the same experience, and am only listing what helped me because I have never seen it mentioned anywhere, and stumbled upon it myself after decades of

I have had the same experience, and am only listing what helped me because I have never seen it mentioned anywhere, and stumbled upon it myself after decades of trying everything: For me, it seems to be the combination of 10,000 IU vitamin D before 10 am, and >120gr protein taken at evening. I am approx 85kg. The protein is the more important component - it improves things considerably but not fully. For more than 20 years into adulthood, I was eating approx 50gr of protein per day (being vegetarian, you have to be deliberate to got more, and I wasn’t). Since this discovery, life has several times taken a path that for a while made deliberate meal planning a luxury, and every time my protein intake dropped, so did my ability to fall asleep at regular hours.