What kind of footage do you have to work with? Can't tell you much without knowing that......
You are potentially getting stroboscopic effects where the frame rate and the offset sync up the same way timing light stops the crankshaft on an engine.
Perhaps a more efficient way to do the effec would be to add directional blur and some color grading to push the highlights toward white.
Dave: I'm using a still tiled image.
Rick: I've tried using directional blur to help the effect but it still doesn't appear to move fast enough. I've also tried putting a wiggle effect with a fast frequency and high amplitude and that actually get me closer to the effect but I can't slow it down momentarily like I need to.
Try creating a comp that had three copies of your footage as three layers. Position the top layer at the center of the comp, the second layer line up with the left edge of the top layer. The third at the left edge of the second. Parent the second layer to the first. Animate the position of the first layer so that it moves to the right side of the screen while dragging the bottom copy with. The move should take say 2 seconds. Set the comp duration to 2 seconds.
Nest this moving comp in in your main comp and enable time remapping. You will see a keyframe at the start and a keyframe at the end of the comp. Move the the last keyframe and set a new keyframe by pressing the diamond in the keyframe indicator. Move back one more keyframe and set a fourth keyframe. Now delete the keyframe at the end and add this expression to Time Remapping:
Now extend the out point of the pre-comp. Your nested comp should loop continuously.
Now pre-compose this comp and enable time remapping again. Make sure you move all attributes to the new comp. Go to the last keyframe, back up one frame and add a new one. Delete the last keyframe. Now move the first keyframe to where you want the fast pan to start, then move the last keyframe to where you want the fast motion to end and enable easy ease by pressing f9.
You could compress 30 seconds of pre-comp to 10 frames or 20 frames and you should have your effect. Throw in CC Force Motion Blur and you should be good to go. You'll still run into stroboscopic effects causing the motion to move forward and backward or possibly appear to stop in the middle, but the blur should help sell the effect.
Here's a sample project CS6 using solids. Just replace the solids with your image and see what you think. (Note: Dropbox may add a .txt extension to the .aep file. Just remove it and you should be able to open the project.