Hi.
Next time when the fridge stop cooling open the freezer and listen if the fan is running.
Make sure that the compressor is working at this time.
If the evaporator fan is not running - replace it
Part number: 482731
Here are the breakdown diagrams and
Replacement parts for Whirlpool ET18JKXRWR0 Refrigerators* | AppliancePartsPros.com
Simon.