I bought an 05 E53 2 months ago (with the nav system) and the radio sound cuts in and out (and sometimes just gets louder for a split second-very annoying!). I took it into the dealer and they replaced the radio and it's STILL doing it! Anyone else had this issue?? It doesn't lose the frequency, it's internal. Sometimes it even makes a "fluttering" sound. I know it's not the frequency b/c my 05 3 series never did this and I've lived here 18 years with the same radio stations! argh!