If your camera is the same as my old Canon HF11, there's not a single thing you can do but get a GoPro type of camera.
The camera itself (well, my HF11) has a floating lens, which basically gives you a reasonable smooth image when you're walking around for example but it cannot deal with the high frequency vibrations in a car. Even if you switch off the stabilisation function in the menu it won't help.
The only way to do it is to isolate it from connecting to the car directly, and I couldn't be arsed to engineer something so I bought other cameras.