At 8 am in about 10 degree cold my coolant light came on. I pulled down my driveway, a steep hill, and noticed it. I stepped out of the car for a second, went back in again, and it was already off.

Should I be concerned?

The coolant light sensor is in the plastic bottle you put antifreeze in. may be a little low. fill slightly above the fill when cold line,then watch for the next couple of days. If it drops at a constant rate there is a leak somewhere. If not your ok for now. Hope this helps. Later... Mark.