Ford Edge Chrome Clad wheels costing you money?

great danger there. dont go fast.
can be tires out of balance (tire weighs feel off)
or wheel falling off (ever check the lugs)
tire bad. (bulged, delaminations , man killer tires, like Firestones)
tire rods balls, ready to fall off (more man killers)
ball joint ,ready to fail. and far far worse...
why not get the car serviced, have them check it out before.... bad happens.
noise and vibration or shaking on any machine means , doom is coming. in most cases,.

The whole vehicle shaking or an engine kind of shake?
The whole vehicle shake could be the tires need balanced. When they are out of balance they can clear up as the speed increases.

your wheels more than likely needs to be balanced one or more are out of round if you had the tires rotated before the alignment this would make the vibrating more noticible.but balancing should solve your problem.

Try balanceing the tires sounds like you lost a wheel weight, after it's been balanced ask a tire man to see if you have a tire seperated, you will see dimples in the side wall if that has happened and is a common problem and should be under warrenty.

Have you considered that the belts in a tire may have slipped or needs to be balanced? Swap each tire with your spare. tire until you find the problem.