Car rattle at neutral.
 

I've been leaving around 2am these past few days to get some stuff done for Christmas and I noticed when I'm at a light and the car is at neutral..RPMs around the 700... and I rev my car a little...I feel the engine shake as if it was about to stall till it reaches the 1000s

Could this be cold related?

Update. It also happened when car was fully warmed up during the day.
Rattles when in neutral, RPMs around the 700. Rattle goes away when the RPM reaches the 1000+

Do you mean when you tap of the gas pedal, the RPM drops to 500 and shudder, and then revs up to 1000+? If so, then it happened to me a several times. But if you're talking about the car rattling when RPM is in between 700 and 1000, then mine does not do that.

My RPMs do not drop. The movement between 700-1000 is when the car shudders and only in neutral.