Lack of Motivation

I've fallen into a funk. Ever since I accomplished my goal of completing a half-marathon, I've loss the motivation to run. At first I thought I just wanted to take a rest from running to let my body recover from the half, but it's been 4 weeks, and I still have no motivation to start running again. I think that if I just get out the door in my work out gear and start running then I'll be fine, but the problem is finding the motivation to actually put on the running shoes, shorts, and t-shirt in the first place. Perhaps I need to create another goal to get myself running again. Maybe a marathon?