Drivers seat heating up w/out heated seat option available on 2011 Subaru Impreza

My 2011 Imprezza does not have heated seat option BUT the drivers seat started heating up 4 days ago -- even over heating. How can this be? Will it drain my battery? I did start using a rigid plastic "back joy" car seat posture support a month ago.

Asked by for the 2011 Subaru Impreza