welcome to the forum.
It might be helpful if you post a little more info...what type of fridge, perhaps what RV it's in, etc....
then someone with knowledge or experience will chime in with better info.
That says, odds are you don't have a frost free fridge. Also the more the door is opened over time the more humidity can enter. my RV fridge does not ice up over a typical weekend, but I did have a noticeable amount at the end of our 19 day trip last summer... a typical electric/gas RV fridge