Is it possible to negotiate a better car loan rate after signing?

I’m wondering if, after signing a car loan agreement, there are any opportunities to negotiate for a better interest rate. Are there specific steps I can take or conditions that might allow for this? Any insights on how to approach this situation would be appreciated.

I think once you’ve signed on the dotted line, the rate is pretty much set unless you refinance later? But I’ve heard that sometimes if rates drop significantly soon after you signed, you might be able to talk to your lender about refinancing without paying too much in fees. I’m not entirely sure how common it is, though, so it might be worth asking your lender directly or checking with a financial advisor.