HI! It is a little understood phenomenon, but the burst of energy you feel is due to the peak of hormones that occurs just before they drop, causing the start of your period. This sometimes also occurs in women who are about to give birth....called NESTING. This is where for some reason, out of nowhere, a woman (very near her due date) suddenly has all sorts of energy and flits around cleaning, preparing and organizing. For the complete lack of motivation youfeel after your period starts, this could be related to low iron (anemia) or dehydration. I suggest you focus on drinking at least 8-10 glasses of water everyday (especially near your period) and taking a multi-vitamin with extra iron everyday (or at least for the week before and during your period) to see if this helps.
Let me know if you still need mroe information! Donna RN