When I'm teaching, I say "again" probably every few minutes. I wonder if my students have picked up on it! I do it for a reason though.
Let's say I just taught the Pythagorean Theorem. I KNOW for a fact that there are students who didn't pay attention when I explained it or didn't quite understand it the first time around. So as I explain it again, I start off by saying, "Again, make sure you remember that the hypotenuse is opposite the right angle." I don't want the students to think I'm repeating myself without knowing it. I want them to know I'm just teaching it for the second time or reviewing it.
Haha, it does take people many times to hear/learn something until it is stored in memory so it's for their own good! I just notice the "again" thing myself, and sometimes I inwardly chuckle.