wheel shimmy-in turn

I don't get a shimmy going straight but if I hit a bump in a long fast sweeping turn the wheel starts to shimmy and will not stop until I slow down. I had the wheels balanced but no help. Car is 94 fwd with 85K miles.
Could it be shocks? No leaking and it feels firm. Tires near new.
Thanks in advance. I haven't align it in a couple of years.
Ray