2004 Raido volume goes up and down on its own

Was at the dealership 2 weeks ago to have battery replaced and they didnt see any codes and i want to know if i am able to get codes to check this on my own? Also it reads on my radio screen Alert need to know what this means? Want to know if anyone else had the same problem.
thanks

Check the owners manual if you have it, most gm made vehicles factory radios have speed controlled volume. The faster the vehicle is moving, the louder the radio