Hi Ruth, I'm in the same boat. I actually enjoy working out and used to be quite fit, but over the years I've lost motivation. I have started several fitness programs, but all it takes is a few days of being lazy ("I'll work out tomorrow") and pretty soon I'm right back where I started.
My motivation: I looked back at the last 7 years of my life and thought about how sluggish I've felt, how many times I've felt self-concious about my body, and how many times that has prevented me from doing something. Every time I feel myself slipping back into old habits, I remind myself that once I get on the treadmill or get through my first set of weights I WILL feel better, and I will thank myself later.
There is nothing worse than sitting in front of the TV with a bag of your favorite snacks, thinking about how you SHOULD be exercising instead. It's depressing and self-defeating because you know you could be doing better. It's a lot more satisfying to sit my butt on the couch and watch some TV after I've had a tough workout--then it's guilt-free
I hope you are doing well and getting closer to your fitness goals!