Prompted by this question I got to thinking about the placement of the word now.
If it’s placed before the comma, it refers to an immediate condition:
You don’t want to answer this word-placement question now, do you?
You might want to answer the question, but the situation is not urgent. You could answer it tomorrow. In fact, it might preferable to answer that question tomorrow if, say, it was your lawyer talking to you and your answer was going on the record.
But if you place it this way,
You don’t want to answer this word-placement question, now do you?
it hasn’t anything to do with time. Now functions in a different capacity, but I’m not really sure what that is. An interjection, perhaps? Something else?
The meaning of the now of now do you? is not Semantic but Pragmatic. It’s what’s known as a Discourse Particle or Pragmatic Particle in the trade. It’s called a Conversational Management Marker in this paper. (Very boring terminology, I agree. Science is like that; at least it’s not in Latin.)
This particular now is often associated with (any combination of (images of)) a shaking finger gesture, a sneering facial expression, and a taunting intonation curve, together comprising a potential off-record face challenge, to put it in terms of politeness theory, one of the branches of pragmatics.