OK. What is happening is normal until you gain control. Try this. Needle down when you stop. Readjust your hands to get control of the piece. Hold it and let the needle go up and down a couple times until you feel you have control and then start moving out. Dont be timid about getting the machine to your comfortable speed before you move out. The problem is you are moving the quilt too soon and the first stitch is jumping. Nothing will happen if you just quilt in place a couple or three stitches. And then when you are quilting make sure the machine stays at a constant speed.
Also...........the important things is to learn your comfortable balance between the speed of the machine and the speed of your hands. Find your comfortabe speed and then adjust movement of hands accordingly.
To do then.....take the thread out and just hit the pedle until you feel comfortable with the sound and speed of the machine and then adjust the hand movement. When you stop be sure to have needle down and down and don't move hands until the machine stops. And as you are quilting "avoid dog paddling" - that is trying to keep the quilt moving...when you feel you need to move hands or loosing contol of the quilt......stop, needle down reajust and then continue as above.
Practice, Practice, Practice is necessary for good machine quilting but you have to practice correctly otherwise you are making the same mistake over and over.