Grinding noise, will not start?

Just about a month ago, my car was making this same grinding noise when you turn the key to start it. I put in a new alternator, starter, and finally when I placed a new battery, the sound went away, and it would start. A month later, it’s doing the same thing and will not start. I don’t know if this is specific enough, I don’t know much about cars. Just looking for some advice on what else could be causing this.