I drive a 1995 325is (Canadian).

Recently on a very cold day the "check Engine" light on the dashboard
came on. I didn't think much of it since I Know the car needs an oil
change. I always have it serviced when the oil light comes on and take
very good care of the car. Later that week the check engine light went
off. But about a week later it came back on and has been on ever
since. The book says the car is drivable, but to have it looked at
asap. What could this be? Any help is appreciated. Thanks.