I've been flying my new Phantom 2 every day for the few days. I noticed something different on the third day of flying. My normal procedure is to wait till everything is warmed up and I have the slow blinking green light. I'll wait a few more seconds then pull up it into a hover. I'll let it hover in GPS mode to make sure it is stable. Yesterday it did something a little different. The phantom was positionally stable while hovering about 5' above the home location but then it started to shiver. The motors were changing speed and it looked like it was shivering from the cold. My normal helicopters will do this same behavior if the servos on the swash plate chatter. Obviously that isn't applicable to this bird. I pushed the stick forward a bit and it settled. I let it hover again and it did it again for a few more seconds then it stopped. I didn't have any problems flying out 2 batteries. I didn't see it do it again the rest of the day when hovering. I brought the Phantom in and connected it to the computer. The IMU and compass values were well within spec. Just to be sure I ran a CAL on the IMU and the Compass. Nothing really changed there. Today I go out to fly and pull it into a hover after warm-up to check for stability and it does the same thing. This time I leave it alone and it stops after about 20 seconds. I'm not seeing any unusual drifting while in this fist hover. It is drifting around what I think is well within the 2.5m accuracy from the GPS. Is this normal? I suspect this is caused by a cold IMU. I'm probably a bit paranoid after reading about these things taking off on their owners. I've checked the props for dings and they are perfectly smooth and straight. I've not crashed it or bumped into anything yet. Thoughts?