I currently work with children ages 1-6 (through play therapy). I am working on my masters in psychology and can tell you that in order to answer this question more information is needed. Such as the age of the child, if he has siblings, is he living in a single parent home? Your grandsons background and history is important, these give clues as to why he behaves the way he does. Also if he has any health issues or had any when he was born? When it comes to a child, environment is everything and of course alot of information is needed in order to appropriately evaluate and assess the situation. Without all of this info one runs the risks of psychopathologizing. This means a giving out a diagnosis only for the sake of diagnosing. It is a form of "labeling" a sickness or saying that something is wrong with someone when it is actually nothing wrong with them. Psychopathologizing, in particular, can devastate a child's life. Please update your question with more detail, or even better, seek a trained professional that specializes in working with children. Such as a child psychologist or school psychologist. Within one meeting with you they may be able to explain what your grandson may be experiencing and how to help him.
Work as a school therapist in a preschool for my masters degree in psychology (practicum).