Maybe a bad connection somewhere, check your ground make sure its not loose, check connections on amp and back of head unit. Just make sure everything has a good connection.
it has something to do with how the ground wire is installed. my freinds alpine's would punch everytime he changed the song. and its was because the ground wire was barely connected.
my alpine amp does that... but then again the mrv-1507 has always been poked fun of because of its loud turn-on noises... but look at it this way, it hits harder than mike tyson ever did