2004 VW beetle makes the "dinging" bell sound while driving but my doors are all closed
is the seat belt light on? It could have a bad sensor in the latch that is tripping the bell.
if it does this when hitting a bump or in rainy weather then its the courtesy lamp door switch located in the door jam/post, you can try disconnecting both of these jam switches and drive the vehicle for a few days if the "ding" is gone replace the switch they are fairly cheap from your vdub dealer.
Search Volkswagen Beetle Questions
Volkswagen Beetle Experts