a little bumpy
Are the tires properly inflated? Are the wheels/tire properly balanced? Those are the most obvious, and likely.
Beyond that you have the driveshaft-unlikely for the most part at only 80mph cruising, IMO. Also, you could have some suspension issues, perhaps engine/tranny mounts, etc. It would help if you described what "alot" is, and where you feel/think the shaking is coming from.

