Probably best to change starter solenoid as it is sticking on apparently. Either sticking with heat or contacts are trying to weld themselves together I imagine. If not changed good chance of starter cranking until battery discharged totally one of the times you try to start car. Then you may get the chance to change the whole toasted starter assembly. Since there is no predicting where and when and if this may occur I would change the solenoid now. You were probably just lucky to get a warning the first time. Never had this problem on european starters but on domestic starters two times with destruction of the starter by overheating from the constant cranking.