Mike Batchelor offers a free preset tool, EasyLINE for Cinema 4D. EasyLINE, as the name suggests, offers you some tools that will allow you to easily animate lines, both linear and bezier with controls for animating the length of the lines, and the size.
You can even add global position objects to control where the ends of the lines are in space. EasyLINE for Cinema 4D is offered as a free download, and is available at SlouchCorp here, EasyLINe for Cinema 4d Xpresso Driven spline tools.
