Professional :: Animation Optimization For Mobile (Running In Slow Motion In The Beginning)

I have a project for mobile where some of my animations scenes look as though they are winding up or playing in slow motion (from the start). They start out slow for about three seconds, as if they are winding up or in slow motion, and then they run at a normal pace. It only happens on specific animations and is consistent on different devices. Also, once I come back to the scene (revisit), the animations run normally from start to finish.

I have had some success in speeding up some animation by doing the following: In some scenes, the following would occurr: 1) a character was walking 2) the character grew in size though tweening 3) the background was animated as well ect. In other words, there were several things happening in the animation. In this example, I made it less complex by keeping the character the same size and making the background static. This helped alot. However, for the aforemation animations, I have tried everything (I am aware of) and nothing has helped. I'm not sure what to do next.