So what CooperMan is referring to is the propensity of Morgan's to get a bit unsorted and violently shake - mainly at the scuttle, as the resonance propagates through the chassis.
Cooperman is also correct that the causes, and solutions are an ENDLESS, point of discussion...you could write a book...
My advice to you is to enjoy the car - if you feel it shaking again, slow down and stop...then head off again on your merry way. With that said, it seems like a bent strut could set up the conditions to start The Dance...try replacing it first before anything.
It is scary when it happens though...
