Slight wheel vibration
 

I just had all four wheels balanced on the 2001 C4 after feeling a slight virbation in the steering wheeel above 70. After balancing still happening now wondering if it might be shocks or other suspension issue.
Any advice is appreciated.

Bad tire? Non visible damage possible. Check the manufacture date on the tires. Usually the last four of the DOT number. WWYY week year. How many miles?

Tire place said there was slight wave in the front tires which may be the issue. The car has 35k miles, bought it with the current rubber (Pirelli p-zero all season).

Do you have directional tires? Check the fronts. It's possible one of the fronts may be rotating in the wrong direction.

If your car sits for long periods the tires could have gone square, some tires are more prone to this than others, I had the same symptoms as you describe and this was the cause

May be the issue?

Did the tire place use load force balancing?