Strange Engagement Vibration???

Hello all. I have a 2013 Prius. I'm new to the whole Prius thing but really love my car so far. I have had a issue from day 1. I have asked around and everyone has told me it is simply a Prius Quirk and that they all do it. I have also taken it to a dealer who said the same thing and that nothing was wrong, but I thought I read some where that it could be a CVT issue or bad transaxle fluid.

When I start to roll under power for the first 1mph it sort of does this weird little vibration. The more I drive in a day it becomes slightly more pronounced. It is very minor but worries me. Is this something that should worry me?

Thank you!