Something that's unable to move or moving without much energy can be described as inert. Wind up in a body cast and you’ll find yourself not only itchy, but totally inert.
When motion is restricted or sluggish, or when something or someone appears lifeless, the adjective to use is inert. A dog who's playing dead is inert, as is a really boring movie. Or for those of you paying attention in chemistry class, you may have heard of inert gases — those elements that won't react with other elements or form chemical compounds.