Nero isn't the best Audio CD burning app.
For a free one that works well try Burrrn (www.burrrn.net).
What media are you using & what is your burner. Note that some DVD burners aren't the best CD-R burners.
I've found that it's important to use quality CD-R media for car stereos & I only use Verbatim Pastels & Super AZO. Mine is a very picky player & I have to be very selective about the media I use.
Also burn no faster than 24x.