Any motivation tips?

Try doing what's usually a lazy activity like watching TV while performing simple exercises, aerobic or reps with light weights. One of the reasons I got back into the swing of exercising after the holidays was on my Wii Fit I could walk or run in place while watching a 30 min show and my pace would be accounted for. But you don't need Wii Fit for that. I get my heart rate up less easily now so I've had to go to the gym more for higher intensity.

Get some kind of step like they use in a fitness class and do step ups. You might even be able to find something in your house for this purpose, like a stool. I felt funny when I'd jog in place but as long as you are bringing your knees up a little higher, you'll still get a decent workout.

When my mom had knee surgery, she got one of those pedal machines (not sure if that's what they are called) to make sure her knee didn't stiffen up but its almost exactly like a gym stationary bike as long as you are sitting in a simple chair. Most have a little knob to increase the resistance, so I do that when I don't feel like step-ups or jogging and can't make it to the gym.

Also if its just a matter of challenge or having fun, sign up with a fitness dance class or unconventional workout class. About 3 or 4 years ago I took my first Zumba class and loved it! Plus there's a group atmosphere and unless you're in a class for all fitness buffs they won't be much better or worse than you are at the exercise. Once you get used to really working out again you can just make it part of your day without needing a mindless distraction.

Sorry if this reply is long! but I've been where you are lacking motivation and these things helped me.