2018 CHEVROLET EXPRESS Structurebody Problems

Since purchasing this vehicle in 2018 we have had an ongoing issue of the car randomly going into a violent shaking when exceeding speeds of about 60mph, it happens without warning, and other than coming to an almost standstill, it is impossible to recover the vehicle. This is extremely dangerous on the freeway. Have taken the vehicle to Chevrolet dealership multiple times without any resolution. They would charge us for an alignment and this never fixed the problem. This continues to be an ongoing issue, and now having researched it on the internet, I am reading this is not a unique experience by Chevrolet/GM truck owners.