Seeing this post really late, but I had the same issue occuring in Nov and Dec...dealership had recently serviced it andI was stumped. They topped off the coolant and I have not seen the problem since. I was certain it was full before i took it back in.
I was sure it was a bigger problem, like the switch or sticking thermostat....but it just took on more coolant at it has not happened since the first week of January. 0 cost
Hope you found a fix since you posted