This is a notorious problem with Samsung residential refrigerators. It is the cooling unit in the back of the main side freezing up. To access you have to remove everything from inside, remove the panel on the interior back, and check for ice build up inside the compartment. This is a major design flaw with Samsung refrigerators. I had this happen on multiple occasions with a Samsung residential fridge.
If you are still in warranty, get any work done under warranty NOW! Mine was out of warranty and cost me hundreds of $$$ to try to resolve, and it never got resolved. Ended up replacing.
YMMV, but be aware that this is a common problem with Samsung residential refrigerators.
