Suspension Torsion Bar problems of the 2019 Ford F-250

On three different occasions within the past month while driving at highway speeds on smooth road surfaces , my vehicle began violently shaking making it almost uncontrollable . Initially I assumed I had a blowout and slowed and pulled off to the shoulder . Once I slowed to less than 20 mph the shaking ceased and my truck felt normal . I resumed my drive without issues. The last time this happened I was going 70 mph on a crowded urban tollway and was unable to slow down immediately due to heavy traffic . The truck is not drivable at guest speeds and I was fortunate to be able to pull off the roadway and avoid an accident. I have a 2019 Ford F-250 just over one fear old that has never been driven off road or or modified . I called my tire dealer and he said this was common. People are going to get killed if this isn't investigated! it feels that the front suspension /steering get in to some sort of resonance that builds rapidly and will not stop until speed goes below about 20 mph. Each time this occurred at guest speed of 70-80 mph. I have an appoint to have a torsion bar placed mext weekend as my tire man says this is common and will fix it. I should not have to pay as my truck is under warranty.