Mine was doing that last week after a long tow.
The thermister (a white plastic clip at the end of a wire) had fallen off the cooling fins at the back of the refrigerator compartment.
Clipped back on the far right (my right) fin, problem solved.
The thermister shuts off the cooling unit when the fridge cools to 35 degrees or so. If it falls loose, or fails, the cooling unit runs continuously.