Floating suspension

Hello, I am planning on buying a 99 Gst FWD this week and I had a question about the suspension, I am a newbie when it comes to suspension. This car seems to float kind of like a Cadillac when hitting a bump but it’s just the rear suspension that floats the front stays steady. And when hitting a bump taking a turn it feels like the rear end is going to get away from me. The car is stock and has 650000 miles, would I be correct saying that it is the shocks that are worn out and not able to handle/control the spring rates anymore, or could it be the rear trailing arm bushings are worn out or seized? I would greatly appreciate the help before I buy the car thanks again.