My car has a USB port for playing music but has very basic control options. I will love to have a shuffle option, is very boring when you know what song is coming next. I have an arduino uno . Any suggestions 
. Thanks for the help.
The Uno USB port is a dumb serial device, while your car USB port most probably will expect a storage device (containing music files). You'll need at least one of the bigger boards (Leonardo...), with a programmable USB port, and a library that implements the USB device type expected by.your car.
Remains the question how to get the music into the controller. A second USB port is not feasible on such a board, you'll need either a second controller for that other USB port, or a different device (SD card...) holding your music files.
Once the hardware issues are solved, how would the controller know which file or track is played by the car, or how would it tell the car which one to play?
Finally the achievable data rate must be high enough, to transfer the music data to your car for uninterrupted playback.