I periodically get an ABS warning light during the summer when I run errands. It usually happens if I have been driving the car around town for a while, stop the car to run quickly into a store and then restart the car. If I stop the car again and it cools off sufficiently, the light goes away. The consensus was that it is related to the quality of my brake fluid and is temperature related. I do not get this happening in the fall and winter months.
ABS is never a big deal, until you need it in an emergency. Then it can become a very big deal very quickly. Personally, I would want to replace it. Here it is also a failure for the statutory motoring test.