Corolla has starting problems

Hello! I have a Corolla 1.4 Bj95 with 88hp. Sometimes the car has the problem that it doesn’t want to turn at all. So I plug the ignition key in, turn it, the lights go on but otherwise it doesn’t make a sound! So the starter doesn’t turn at all. Now my impression is that the starter relay has a Macke. Can anyone tell me where this is? Another thing is that the car has a retrofitted immobilizer. Can they react like that? Greeting, Michael