grinding noise

My 2003 2.4L Accord is making a grinding noise that isnt quite constant. More it makes the sound for a second, then is quite for a second. I have looked at videos what a bad alternator bearing sounds like and its very close to that sound. But what i dont understand is why would the sound start...

Ok, so sometimes when i start my car i get this whining/grinding noise straight after the engine turns over for a second or two which i have a feeling might be my starter motor. Not really sure how else to describe it. There are times where it makes the sound while trying to start the engine...