This is a potential complement that expresses you "can't do something." Don't confuse it with 不懂 as explained in The "-bu dong" (don't understand) Potential Complement.

Structure
The potential complement 不动 is used to express lack of physical ability to do something. This can be used not only with actions like walking, running or climbing, but even actions like eating and chewing.
It is used like this:
subject+physical action +不动

Examples