Recently I've had a tendency to fall asleep after supper for an hour or two, then wake up for a few hours, then go to bed. In some ways it's unhandy, but I figured if it all adds up to eight hours or so, it's all to the good. I know several people, including members of my family, who have talked about a similar sleep pattern. So I googled, and found plenty of articles about "bimodal sleep." It's a thing.