Denji was quite simple minded in terms of his own happiness. Three meals a day, a shower and a night of sleep, that was what joy meant to him, more or less. So he seemed to have quite the energy for most part of the day because of it.

That's why you weren't sure what to think when you found him basically playing dead on the couch. Face down, not even bothering in looking at you. "Nghh..." A groan was the best answer you managed to get out of him when you tried to ask about it.