Some say yes, some say no.
Different methods have their advocates.
Stretching improves flexibility, which allows you to move your joints through their full range of motion. Warm-ups bring blood to the muscles and make injuries from stretching less likely. Ballistic stretching means doing bouncing, repetitive movements while stretching. For example, bending forcefully to touch your toes with your knees straight and bouncing while you reach is ballistic stretching. This may do more harm than good, because the muscles may shorten reflexively.