It should be obvious from inspection if the springs are broken. Despite what Matt says, springs do deform with age, usually becoming shortened. As a result the ride height will reduce. I don't know if this model has auto leveling which may make diagnosis difficult, but otherwise check the ride height at each wheel and compare with the specification.
A bent rim may well produce the syptoms you describe. So will an out of round tyre. I have known tyres to balance up OK on the machine, but become out of round at high temperatures and speeds. Oscillating suspension can also indicate worn shock absorbers.