Temp gauge

Lately this winter I noticed something on my 96 S-10 ZR2 that I don't remember happening last winter. If I start my truck and let it sit for 10-15 minutes to warm up, the temperature gauge climbs up to around 210, which is the middle line. Usually, it doesn't get any higher than the first line. I just noticed this morning that it did it while I was driving, but it went back down to normal. It hasn't gone above 210 yet, but could this be a problem? If so, what could've caused it and how would I fix it? I think it might just be a faulty thermostat(hopefully). Let me know. Thanks