LG refrigerator stops cooling but starts working after unplugging

LG refrigerator stops cooling but starts working after unplugging LG LFX25976ST/02 stopped cooling several months ago. We unplugged to wait for repair tech. When we plugged it back in, it started working again. This happened 3-4 more times within the first 2 weeks, then consistently worked for 3 months. Now, it seems to have quit for good. How do I troubleshoot this?