I am 71 now and for the last couple of years I normally sleep about 4 hours then up for a bit then a couple of more. I have been told that is a common event in us elderly.
The idea of eight straight hours of sleep started with the Industrial Age. Before then it was common and normal for people to wake after about four hours, get up and do simple things, then go back to bed for what was called "the second sleep." We old farts tend to be less tied to society's schedules and can sleep whenever and however suits us, and what suits us might actually be more normal for humans.
Im a night person naturally so that will work out fine. I still do it at times now at 65 yrs old.