You didn't mention if it occurs at all driving speeds or just at highway speeds, or how many miles you have on the car.

My checklist would be the following:
1. Bounce the 4 corners of the car one at a time and listen for noises.
2. With the hood up, grab the 3" metal top of the strut mount and see if you can twist it or if it is loose. (compare drivers side to passenger side)
3. Put the front end up on jackstands, get under the car and started pulling and pushing on stuff to see if anything was loose or broken. Also remove the front tires and do the same.
4. Don't forget to inspect the CV joints for torn boots also.
5. Balance all 4 tires.
6. Take it to the dealer for a full 4 wheel alignment and have the mechanic look at the suspension.

If it is something that is new that happened all of a sudden, then i would suspect either something broken, or that a wheel weight came off. If it has come on gradually then something worn out.

I have one road that I drive on that makes my car feel like it is falling apart. It is only that one road and only for a few miles.

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Nathan Valles, Black 855R, Tint