It's bouncy and very jerky, but IMO there is a smoothness to the bumps and jerks because it is a polished, modern ride. It doesn't feel painful to me like some wooden roller coasters (the teeth chattering kind). Every jerk and bump is intentional, and in a way to me they feel smooth.
Ever since I was in middle school, I had recurring muscle spasms in my neck that have NEVER been triggered by a ride on Dinosaur (I've probably ridden 20-30 times). My father also has neck issues and has been completely fine on it.
I could see how someone with neck or back issues could have a problem on it, but that hasn't been the case for us. Everyone's body and tolerance level for this kind of thing is different.