I would recommend reading Dr. Harvey Karp's Happiest Baby on the Block. My daughter used to have a really hard time sleeping when she was a baby and I used that method to get her to sleep and it saved us. One of the things he says is to shake/jiggle...you have to do it hard enough that the baby's head jiggles a bit from side to side. I used to put my daughter in the stroller and then shake it...it seemed like I was shaking it REALLY hard, and most people thought I was nuts, but her head only moved a couple of centimeters from side to side....not a huge movement. And it was the ONLY thing that worked with my daughter and I was the only one it worked for because no one else dared to do it hard enough. But my daughter is now almost 7 and she's reading 2 grade levels above her age, scored in the top 20% of kids in the country for math, reading, etc...so I'm pretty sure she's not brain damaged or anything. But that book describes the motion and what's safe, etc.