The last few days I've noticed that when my 2010 Honda Element EX is started for the first time after a while, like overnight, I hear rhythmic popping noises from the stereo. It does it on both FM and Aux, and keeps going even when you switch inputs. It goes away in less than a minute or when you adjust the volume, but I'm worried since I just got this car and haven't had this issue before. Any ideas what it could be?