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.
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.