If the freezer section seems cold, but not the fridge
In refrigerators, it’s the freezer that primarily receives the compressor’s cooling action. To cool the refrigerator section, the designers put a little duct from the freezer to the refrigerator section, and put in a fan. While the refrigerator section may have temperature buttons or dials just like the ones in the freezer section, they do not actually control direct cooling of the refrigerator. Rather, they merely control the speed of the fan, or work the flap in the duct that controls airflow to the refrigerator section.
For the refrigerator section to cool well, it needs all three components of the cooling mechanism to work well — it needs a freezer that’s cold enough, a fan that works well, and a control flap that’s open wide enough. Sometimes, in winter, you may set the freezer to a moderate temperature level, and then forget all about it come spring or summer. Then, if the refrigerator doesn’t seem cold enough, it’s only because you forgot to turn the freezer back up, or turn the flap to a fully open position.
And then there’s the fan
If you live in a humid area, there’s something that’s not really in your control that can affect how refrigerator works — the humidity could condense on the fan, form ice crystals and cause it to run erratically. You might consider moving the refrigerator to a room that has air-conditioning so that you don’t have as much humidity.
If your refrigerator doesn’t work well in winter
If your refrigerator is in an unheated part of the house in winter, this could be bad news, too. Not only could water freeze in the drainpipes conducting condensate away from the interior, the compressor could have trouble working for long enough periods, too. You need to relocate your appliance.
If your fridge is on carpeting
Many refrigerator models have their condenser coils at the bottom. If your refrigerator is in a part of the house that has carpeting, this can be a problem. The pile can restrict airflow, and also act like a sweater, holding heat close to the coils. You don’t actually need to relocate your refrigerator, though. You only need to put a sheet of plywood or other stiff material under your refrigerator.
Of course, none of these fixes me actually apply in your case. If these ideas don’t work, a qualified refrigerator technician is your best bet.