1) Lifting shoes. You're rocking back and forth because you can't feel it's happened until it's happened. If those are lifting shoes (It doesn't look like it but I could be wrong), then keep your weight on the middle of your foot. All the time. We're serious about this and you should be too.
2) Bend over more, right from the start, but also get your knees forward quicker, and set them by the time you're halfway down (or so).
3) Turn your toes out more, and get your knees out better.
4) Get tighter. Your first three reps were too deep. A belt will help.
5) Stand all the way up at the start, and between reps. Hips and knees fully extended.