Rear vibration

Hoping to get some help diagnosing an issue I have on my 2.5i 5spd. About a week ago my car developed a strange vibration coming from the rear. The strange part is it only happens under certain conditions. From a complete stop, up hill, while the car is still cold from sitting overnight or all day.

My neighborhood has a red light at the bottom of a hill. From a complete stop, shifting into first, pressing and gas while lifting off the clutch. This noise coming from the rear almost sounds like something to do with the load on the drivetrain, however, once the car has warmed up it won't do it. Video linked below. Any ideas would be greatly appreciated.

How old is the exhaust system ?

When was the last time the rear diff fluid was replaced ?

Have the rear wheel bearings been replaced ?

Hard to tell anything from that short video.

Can you get under the car while its up on jack stands with the engine running ?

Could not get a good handle on the noise from that short clip.

Is it purely engine rpm/load related? (exhaust?)

Any noise free revving in neutral? (exhaust again?)

Or is there a component of wheel speed dependence? IOW, if you shift gears then replicate the same engine rpm/load at higher wheel speed, is the noise the same or different? (age/miles on wheel bearings?)

Just to eliminate the obvious, make sure you don't have any loose items rattling around the trunk or spare tire well. Spare, scissor jack, tire iron properly secured, etc.