Some frost free models have a heating element on a timer. Every so often, the refrigerator will shut down, then the heating element will turn on for a short period to remove ice build-up around the cooling coils (which may be hidden from view).
If the heating element/timer is not functioning properly, then ice can be blocking the air flow. Check to be sure air is flowing where it should or if you can see ice build-up through any air vents inside the freezer. Or try sticking everything in ice chests and defrosting for 12 to 24 hours or so with doors open. (There can be a solid block of ice hidden behind a partition and it can take quite awhile for it to melt.)
If the defrosting gets it working again, then the problem happens again in
2 weeks to a month, then ice has built back up blocking the air flow.Of course this all depends on the model of fridge you have, so could be something else.
May want to get a refrigerator thermometer so you can tell if it is cooling properly after defrosting and then be able to notice more quickly if the problem crops back up again.