Strange low speed grinding/vibration while driving my 2015 Mazda6 GT

[Topjack]

I'm not sure if I am having some kind of transmission problem or if what I feel while driving is normal but never noticed it until recently. My Mazda6 GT has automatic transmission and less than 10,000 miles. I am the original owner. No accidents or abuse. Has anyone experienced this or have a clue what might be the cause.
This is not something I hear, but feel while driving at low speed. Once over 40mph it seems to go away.
Note.... I haven't noticed this but a few times.
Any thoughts would be great...Thanks.

 

[Topjack]

Anyone have a clue if this is a problem I'm having or something that is normal??? Any help would be great.

 

[ceric]

Does it go away after some distance of travel?
If yes, it could be the tire spotting.
However, you said "grinding".... in that case, could be the bearing.