2001 Hyundai Sonata P0118 code for

I have a 2001 Hyundai Sonata with under 50,000 miles and the check engine light has come on twice in the last 2 weeks. I took it to autozone and they pulled a p0118 code (engine coolant temp) although the temp gauge was still in the middle. The light went off the same day after about 4 key turns. It stayed off for 2 weeks and then came back on. Again, it went off after about 4 key turns. Is this something to be concerned about? I have noticed that on both occasions when light came on, it was on very hot days with lots of short trips. Please advise.