Asking for input/help diagnose, not an a-body

You really haven't given much info. How many miles ? Condition of car, tires etc... Why not just go to an Infinity or Nissan dealer to get diagnosed. May be covered under a tech bulletin.
If you do find out it is a suspension problem are you able to fix it yourself or get parts from other than an Infinity/Nissan dealer.
over 200k miles, worn out tires, cracked windshield, etc... There is a identical one on a used car lot in the next town. It has a bad trans and been sitting under tree sap for at least a year. Owner wants 5 hun for it. I'm considering buying it for the windshield, decent tires, and more. These grand daughters with their worn out vehicles and Bojanges budgets are gonna break me. But what are papas for? LOL