Frequent muscle twitching and paresthesia, what are the underlying causes of these symptoms?

Depends where,: How often, and what brings it on. Twitching and parasthesias can be caused by numerous things and it would be difficult to speculate with just a little history such as this. It could be anything from dehydration to ms, but we would have to know much more prior to even suggesting a diagnosis. See a physician for a thorough history and physical exam.