For the last several years, I wake up almost every morning after only 4-5 hours of sleep. Then I don't feel right during the day unless I am able to go back to

For the last several years, I wake up almost every morning after only 4-5 hours of sleep. Then I don't feel right during the day unless I am able to go back to sleep. It makes me think that theory of pre-industrial dual sleep periods may be true. It's also possible that I'm just older and have to urinate. Or the reflux issues that interfere with my breathing somewhat need to be cleared out. As far as falling asleep, I have found that Vitamin D3 can help quite a bit, if taken in an adequate dose.