On my way to work, my 2002 Cabrio's temperature gauge was running normal, (it stays around 1/2 way up) and then all of a sudden, as I was going 60 mph, the temperature gauge needle started to go down (towards cool). It went about 1/2 way down, stayed there for about 30-60 seconds and then went back to its normal position. It did this 3 times and then ran fine for the rest of my hours drive.

Has this happened to anyone before? If so, is it serious or just my gauge being faulty?

The coolant temp sensors are prone to fail.