You are one of those who have a biphasic sleep pattern. Basically, this means that you sleep around four hours, wake, then sleep again.
There is a substantial body of scientific opinion that this is in fact the natural human sleep pattern. If you research it, one of the things you will find is that in the eighteenth and early nineteenth centuries, it was so widely accepted in Europe that in cities such as Paris and London, shops and tea houses would open for business for a couple of hours during the night. People would get up, dress, and go out for a walk and to meet others, then go back to bed.
When I reached my sixties, I found my monophasic sleep pattern turning into biphasic. When I wake between three and four a.m., I don’t dress, but I get up, make myself a hot drink, perhaps look at the news channels, or go out into the garden in mild weather. After about 45 minutes, I go back to bed and sleep well for the rest of the night.
