dnd 5e – Can an Aspect of the Moon Warlock choose to sleep whenever they want?

You can sleep if you want.

“Does not need” is not the same thing as “cannot”. This is evident from the feature’s use of both phrases.

You cannot be forced to sleep. This clearly means that no external force can cause you to be put to sleep.

In contrast, you do not need sleep, but this does not restrict your ability to do so. It simply means that you do not suffer any negative complications from insomnia.

As a DM, I just let my players sleep when they want, unless there is some extenuating circumstance preventing it, such as being in a rainstorm without shelter.