I know this is a little late, but I had the exact same issues and the dealer told me that I needed new brakes. They said the rotors had warped enough causing the vibration in the steering wheel. They replaced the brakes and sure enough, the vibration went away.

 

Did you have shaking when you were braking too?

 

Yep. It was a lot worse when braking. If I let go of the wheel a little bit when braking, especially a decently hard braking, the steering wheel would wobble pretty violently!

 

The day after the alignment I changed the rear pads and rotors to no effect.

It is still a world better than it was. I think that I honestly have a messed up wheel.

When they aligned it they rotated the tires to the back and now I have a slight shake in the back.