A Motion to Dismiss your chapter 13 case is generally brought by the chapter 13 trustee. This motion is usually brought by the trustee to dismiss your case, because of failure to follow some sort of provision in your plan or the bankruptcy code.
Commonly, Motions to Dismiss are brought for the following reasons, failure to make your plan payments, failure to turn over tax refunds or other property of the bankruptcy estate, and failure to provide your tax returns.