It didn’t say you have to be a business, it says you have to be a professional seller. That means you need to sign up for a professional account, It’s $39.99/month. Once you’re signed up, apply for approval to sell in the automotive category. I don’t sell in that category so I don’t know for sure, but you may need manufacturers INVOICES and NOT receipts from liquidators.
Car parts have certain liability issues, like people crashing and stuff. Amazon used to be wide open for almost anything but now they’re getting more and more careful. They’re not looking for flippers as much anymore to fill their warehouses. They’re looking for regular sellers who are in that business.