Has anyone experienced the issue of the steering wheel shaking at speeds between 105-120 with the Iveco Daily, and if so, do you have any viable solutions?

What could be the problem if the engine shakes violently upon starting and requires turning off and restarting?

My car is a 3.0T manual, and when accelerating to a certain speed, it suddenly feels like it's slowing down. Can any expert explain why this might be happening?