I seem to always have this problem as well. I used to always tell myself I would get up and work out, and couldn't push myself.
If you have someone willing to work out with you however, it makes ALL the difference. I workout with someone twice a week, at 6am now and the fact that someone is waiting for me is the boost I needed to get myself out.
The days I don't work out with someone however, I seem to lack the motivation to go workout that early, and end up going to workout later in the day. I find it hard to just wake up and go for some reason as well.
The hardest part about working out is taking the first step! I always tell myself if I don't feel like working out I have to at least go and sit on the bike for 30mins. by the time I get in the gym and get going I do a full workout! Just need to trick yourself to taking the first step :) After a couple weeks you will want to go without even thinking about it :)
My best early morning motivation is my dog. She needs a walk everyday! Also, as I work full time and have 4 kids that morning time is really my only peace and quiet so I like to get out early and start my day.
I agree with the suggestions above too. If you have someone waiting for you, you won't let them down. Also, on my days I don't want to walk with the dog, I will do the same as malelia and say I'll just do a short 15-20 minute walk and it always ends up longer!
I understand your frustration. I find it hard to get out to work out. I recently moved into my new place so that has been my workout routine. Unpacking everything. I wish I could get to the gym to workout different areas of my body, but I can't get the motivation too. I think that if I had someone to workout with it would be easier to do, because I have extra motivation with help keeping me on track. I also find it hard to try to stick to my diet, because I have a weakness to almonds. I eat them all day. I go through a pound a day. Sometimes more than that.