I want to start running again, but don't have motivation.?

I ran a half marathon in August of last year and haven't run since! I don't know what my problem is, but I just lost my gusto. Now I am feeling it in my hips and waist! Yikes! I have tried to run on my treadmill, but I have lost my stamina and feel like it's the first time I've ever run! Anyone have a good suggestion for starting up running again? Do I have to start all over with a beginner 5K training program or can I jump back into where I left off? It's been 5 months since I consistently ran.