I've seen it on my friends freshly purchased Zumo 550.
He sent it back. Another one did same. He got money back and bought another make.
There are hundreds of reasons why this may happen, only attempt to get it serviced will tell if it is really problem or just design of Garmin so-called "motorcycle navigators" legalized robbery ( I had chances to compare a lot of PNAs and Garmin really gave me most problems and worst performance).