I took my new-to-us 2011 on a cross country trip this June. The first couple days were exactly as you described. Horrible bouncing and slamming. It hadn't been noticeable in town, but up on the freeways it was terrible.
Did some research and found my tires were inflated by the dealer to 120 PSI. Recommended pressure for my weight was 82! Once I had access to a good compressor I dropped everything to 85 PSI and had a much more comfortable ride.
I second checking your tire pressures.
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