Hello.
I've been told that napping during the day and sleeping during the night is by design.
This is when you click on the need, right ? I've noticed this too.
I think the Nap interaction does not have a bed assigned which makes them use the closest ones.
I agree that it's annoying.
I'll add
It also happens if click on the Energy Need but the autonomous Sleep seems to be dependent on time. I think the Sims will only autonomously sleep if the clock is 10:00 PM/22:00 between 6:00 AM/6:00 (I think), if it's not night, they will either attempt to have coffee or nap regardless how severely tired they are. You must manually command a Sim to Sleep.
This can be annoying if anyone's in my state (Princess Cordelia Single/Galleon Bed or Rustic Dream Bed and/or Sims with Never Weary) where the Sim will have to sleep in the daytime.
