Social security is claiming I owe them money, can they take my car that I own as payment

No... because it's actual value is unknown before it hits auction, and all involved costs have been met and the parties involved paid BEFORE anything went to the debt... would almost certainly exceed the cars value in many cases.

One of the many reasons they want cash...

While I would doubt that the SSA would take your vehicle, if they get a judgment against you and that is your only asset, they might.

You're lucky; not many years ago, your car would be limited to a maximum value. Now it isn't.
You may have "one vehicle, regardless of value, if it is used for transportation for you or a member of your household;"
ONE vehicle.