Steering wheel shaking after 80km/50 miles and hour

Likely time for new steer tires, will be like new after. Did that to me, came out of nowhere, same speed range as you, tread looked good but when I finally took it too the tire shop they could see the cupping right away.

 

Paccar 4 bag air ride on front end by chance?

 

One or both sides of either or both tires look like a roller coaster?

That's usually the cause that happens at that speed.

I get it every time my steers get to that point.

 

Maybe time to replace, steer tires, shocks, bad front wheel bearing, drag link, alignment, wheel out of balance. Not to worry though, it will only cost you a few thousand to figure it out. When doing the process of elimination, it's generally the last thing that you have checked.