Moisture can develop when there’s high humidity, or if the refrigerator has been opened several times in a short period. The moisture should go away when conditions and use return to normal.
You should also check to be sure your refrigerator doors are closing completely. If the doors are open even slightly, warmer air from the room will enter the refrigerator and cause moisture to develop. The door should require a slight tug to open; if it doesn’t, check to see if any items on your refrigerator shelves might be preventing it from closing.