Warning light on dashboard Citroen Xsara W reg 1.4?

Am getting a red stop light in the middle of the dashboard along with a small circle by the temp guage. It happened when the car was started from cold this morning and also beeped but then went off again and was fine again for the rest of the journey. I made another journey half hour later and it came on briefly when the car was started and then again after a few miles. Any help with what this means will be much appreciated.