You probably know a friend or family member who is an avid exerciser and seems to enjoy it. Spend more time with this individual. Allow their zeal for exercise to rub off on you. You'd be amazed at how much another person can influence your life when it comes to exercise. If you associate with people who despise and have no desire to exercise, then you can bet beginning an exercise program will be very difficult.
Even for me lack of motivation is a problem I face occasionally. Often this lack of motivation isn't in the form of getting started with exercise, but rather being motivated enough to have a quality workout session. There is no doubt in my mind that the people who surround me during my workout (i.e., my training partner and others in the gym) can make or break the workout. I have some partners that are great encouragers, while others just allow me to go through the motions without much encouragement. It's a night and day difference when I evaluate the workout after I'm finished.
Make it a point to surround yourself with people who enjoy exercise and have made it a part of their lives.