When shooting at the telephoto end of your camera's zoom range (100mm or longer), the vibrations caused by handholding further magnifies camera shake thus resulting in blurred images.

One way to combat this is to use a camera support like a tripod to stabilize your camera. Another way is to increase your camera's ISO values or use a wider aperture in order to increase your shutter speed. That way, you'll be able to capture images t a higher shutter speed and reduce the chance of image blur in your images.