starter whirring before catching the flywheel

[YOUNG SCOOTER]

2008 Yaris 5 speed manual, 173k miles

So far its only happened a few times in the past week. I havent yet found a specific pattern to it, whether it does it when its hot vs cold, etc. But when i go to hit the starter the engine doesnt turn over, and i can hear a whirring. I wait about one full second and then the engine catches, and it starts up fine. To me it seems like either a tooth is missing off the flywheel, or the starter bendix isnt engaging correctly. I assume its the starter and I ordered a new one.

Is there anything else I may have overlooked when trying to diagnose this? Also I have no clue where the starter is or how hard it is to reach but I assume i will find it somewhere around the bellhousing