The strip of frame that runs between the two doors of your fridge and freezer is called the mullion strip. It exists whether your unit is a side-by-side model, a freezer-on-top model or a freezer-on-bottom model. Behind the strips rests something known as a heat loop. Its job is to warm the area near the door gaskets to keep condensation from forming on the outside of the unit.
If the warmth you feel seems excessive, or is enough to cause the rubber gasket seals around the doors to yellow, you may have an equipment failure. It could be due to a failed condenser fan, or clogged or dirty evaporator coils. Both problems cause an insufficient movement of air so that the hot air inside can't be pulled and distributed away from the heat loop, causing it to overheat.
Evaporator coils are on the back of the refrigerator and are exposed. It isn't unusual for them to collect dust, lint and pet hair. Too much of any of these things can interfere with their job. The solution is to regularly clean the coils using a vacuum with a hose and brush attachment. Gently brush at and suck up anything clinging to the coils.
The failure of a condenser fan may also account for hot spots on the exterior of your KitchenAid refrigerator. It is simple to diagnose as you can hear a working fan running. If you don't hear the fan, call a repair technician to take a closer look. Without a working fan, a heated cabinet is the least of your problems, with the greatest being food spoilage when the unit fails completely.
Once everything else checks out, you may discover that environmental factors are behind a hot fridge. Loading warm food into the refrigerator causes it to kick in and work harder to bring up the interior temperature of the unit. As a result, the cabinet grows warmer for a little while. Temperature and humidity outside may also affect how the unit runs and how warm it gets. The more often the door is opened, allowing controlled air to escape, the hotter the unit runs until it is able to normalize the interior temperature. When you first start up a refrigerator after it has been sitting at room temperature, it will grow warm until it has sufficiently cooled down on the inside.