The temps here have started getting pretty cold - teens to 20's. I've noticed the "check coolant" light comes on after the car has been running about 5 minutes. I checked the level and it seems fine. Car starts right up, doesn't overheat, temp gauge is staying right in the middle. If I shut the engine off and restart, the check coolant light goes out and stays out. The engine does sound rough/louder than usual though (checked oil and that's fine).

Any ideas? Was told it might be the thermostat and needs immediate attention. Bad, bad time for repairs though I was going to get a cold weather check - need to wait another pay or so first. I don't want to risk having a major problem and was hoping to find possible answers here before I call my mechanic.

give your rad cap a look see. It might me a drop in pressure due to a worn rad cap