Also, AutoCAD is used primarily as a design tool for architects, prototype/manufacturing designers, and the like. For 2D-3Danimation, there are far better choices ranging from freeware to industrial strength. If you are new to this, you may want to start off using freeware because (a) you might find out that you don't have the hardware, money, or patience for 3D modeling, or (b) some recent freeware programs can make decent 3D renders.
Try the following:
Sketch Up: One of the easiest 3D tools around. You might not be able to make photo-realistic renders, but you can get your feet wet with this program. This will introduce you to solid modeling (as apposed to vector design). You will get a feel for manipulation in 3 dimensions.
Blender: This is a more serious program, and while is lacks the speed and refinement of the industry's cutting edge programs (Maya, Lightwave, etc), it can produce some remarkable results with a skilled artist. This is a much more complex program that will require a lot of reading and patience.
blender.org - Get Blender