I would start with shocks. Bad/ broken/ worn out one side. Look for heavy oil leakage out of the shock. Other than that get it "up" on something........just high enough you can get under there SAFELY but with the weight on the tires, have a friend "jounce" the heck out of both sides and simply LOOK
Get it off the ground, preferably on a hoist and inspect everything you can think of......including what was posted above
