Good for you on wanting to motivate yourself to workout more! I'm in a similar boat myself, and although I haven't found a "cure" for staying motivated to workout, I do have a few suggestions.
1. Try working out in the morning. Even if you do just a little bit, enough to get your heart pumping, you will set yourself up in a positive direction for the rest of the day. Sometimes I'll take my dog for a morning walk, and I'll experience clarity of thought and ambition for the rest of the day. It's really amazing what one little walk can do! **Don't forget to eat breakfast too, though ;)
2. Change up your workout routine BEFORE you start to get bored. I mean days before! As soon as you even think of getting bored with your routine, you'll lose motivation and proper form. This can have a severely negative impact on your drive to keep working out consistently.
3. Also, don't be TOO hard on yourself if you miss a workout. I try to give myself very little excuse to miss a workout. (I workout at home, so that's not too difficult...).
4. Cycle through interval training. When you do interval training, you're less likely to get bored because you raise the challenge each time and you do different exercises back to back. There are tons of exercise videos on video-hosting websites. I love that I work out in my home for FREE!
5. Make goals and record them on your phone, calendar, the back of your hand... They should be challenging, yet attainable. Make working out "X" amount of times per week a goal and reward yourself for doing so (with something healthy, of course!)
6. Eat healthy. Whenever I eat healthy, I instantly think of working out. Good food goes hand in hand with exercise for me.
7. Last, but not least... Stay positive! See if you can find a friend/family member to workout with you and challenge each other. Cheer each other on!