Starter motor

Hello, everyone

I am having trouble starting the car. This is the second time that happens, the same problem. I think that the starter motor is the causes this.

First time I had this issue I started the car with a bump start in order to get it to the mechanic. As soon as I arrived there the problem was fixed itself, I do not know how but it did. So I decided not to do anything.
Since then have passed four or five months, I do not know exactly how much and it happened again.

When I try to start the car in a stationary position, the starter motor makes a clicking noise.

So I am interested in knowing which is the reason why this happens and where the problem stays.

Thank you very much guys for your time.