2K5E55AMG

Hey guys, have a weird one - when I started my car today, the COMAND unit played a weird chime and everything was muted. I tried the radio and the AUX connection, couldn't unmute. Hit the mute button multiple times and nothing. After a while, it automatically unmuted itself and the radio was playing. Now every time I start my car, the chime plays after COMAND starts. Now sometimes it auto mutes and sometimes it doesn't. I noticed when I turned off my car, it also auto mutes. Any ideas?