Translation:Are you sleeping?
Is this the same as "are you sleeping?" Or does it really refer to asking about their habit of sleeping?
Since "Are you sleeping" is set as the primary translation, yes, I would say so. From what I've learned in my half a year of learning Dutch, I'd think the Dutch present simple tense means both the present simple and the present continous tense in English. It makes perfect sense to me, since it's the same in Czech (my native language).
I'm just a beginner, but definitely not. "Ben jij aan het slapen?" would.