I would focus on a few things.
Tire and wheel out of balance, get them road force balance to see if the tire or wheel are out of round.
4 wheel Alignment.
Shocks are they leaking or high mileage they could be ready for a rebuild. On my truck this is what was causing a similar issue.
I'll try the road force balance.
The truck has 17k on it, no visible signs of anything wrong with the shocks.