A motion doesn't always start at the point that you place the keframe. Let's say that your arm is straight out from the body and you want it to raise to be straight up at frame 120. The software tries to "get ready" for the action by actually dropping the arm before frame 120 to created a fluid motion. It's great in theory, but it can cause unpredictable actions and does not always create the desired effect. Example: You want the arm to raise and wave 2 seconds in, but want no anticipation before that. (perhaps the character is responding to something.) In the animation pallette find the shoulder.(for the purposes we will only use one object) Copy the KF from the first frame and move it to frame 120(Alt Drag). Swipe the two Kf's and click on the "linear section". This should eliminate motion until you place the desired motion until after frame 120.