I used to be big on the old CAAD 4 and 5 Dales. I raced on them for quite a few years.
It was a characteristic of that frame to have lots and lots of 'tail wag'. My team mates used to laugh and joke about it and we all noticed the same effect even with different sizes and fits etc.
They would step out and bounce around all over the place, but always came back and never caused anything more than a few raised eyebrows in the sprints.
We always put it down to the huge amount of lateral stiffness in the rear triangle (them chainstays were by far the meatiest around at the time)
Interestingly, I ride a BB30 CAAD 9 now, and don't notice it to the same extent, It seems much more stable. This would indicate it isn't probably material related, or indeed the chainstays as the CAAD 9 has enormous tubes and bags of stiffness. Probably just a quirk of the geometry.
Could be worth you pulling up a geometry chart and overlaying them to look for similarities if it really bothers you.
Alternatively, just keep riding it and get used to it, alter your technique a little bit to compensate.
What I'm trying to say is......some frames just do that, not much you can do but learn to live with it.