That she does, and Merlin notices that she seems to be having some thought right now, so he's sort of waiting for her to act on it. So for a while, he doesn't move at all but when she seems to not move further than that tilt of her head... Well, how is he supposed to read that?

If she's hesitating, then it has to be something important.

He tightens his grip around her just a bit, moves a foot back and tugs her along as he spins around, slowly, pondering. And... why stand and wonder when you can ask?

"What're you thinking?"