transmission grinding?

Daishi

its only happened a few times i have about 1300 miles on the car i will shift into gear let out the clutch and ill hear almost like a grinding sound coming from the tranny until i shift out of gear.. car still feels smooth dont feel any grinding in the shifter its only happened shifting into 2nd and 3rd and it happens rarely im just having problems diagnosing what it is.. has this happend to anyone before? the sound will occur while moving while im in gear already.. it does not happen while shifting into gear. what could be wrong? this isnt my first manual transmission so i shouldnt be having any issues lol. or is this normal and the tranny is just loud.. its very hard to explain its like a very fast but quiet grinding sound not a loud grinding/crunch sound.

PS: im gonna be changing my tranny fluid to redline MT90 within the next couple weeks, maybe that fixes the issue who knows.. any opinions would be greatly appreciated.

Thanks