01 Security light on, engine works fine

Good day, gents!

My security light was on last week when I drove to work. The engine started fine and everything in car works as it should. After I turned the engine off and started again, the light went away, so I forgot about it. Same thing happened this morning, the light was on, after I turned engine off and started again, the light went away. Once again everyting functions without a problem.

What could it be?

Thanks