Clutch/ tranny vibrating in Reverse
 

First off, I don't think this is the Vibrating Clutch Pedal of Death that occurs right before the engine blows.
When I'm backing out in the morning and letting out the clutch I'll get a vibe/rattle in the pedal. It was harsh enough that my passenger could hear it. When I put it in 1st it goes away. It doesn't do it every time I back up, maybe 50% of the time.
Also when I'm idling at a stoplight in neutral after about 30 seconds I feel a vibration towards the middle of the car that remains whether I push in the clutch or not. This rattle seems to go away if I rev over 1000k.
At first I thought it could be my RMM breaking in and needing to be re-torqued but I checked and it's tight as shit. I have about 6k miles on my car and I never launch it.
Everything feels perfectly normal when driving through all the other gears and I never feel anything weird in the shifter.
Any ideas?

I experienced something like that on a different car, turned out to be one of the clutch springs decided to break free of its confinement. It still drive okay until a 2nd spring broke, then it fought to not go into gear if the engine was on at all.

Looks like a dealer visit is in my future.