I have the same exact problem! I work full time and then go to classes until 9. When I get home, it's more school work until I'm too exhausted to go on so I get about 4-6 hours of sleep every night. It's been such a struggle for me to commute by bike the way I was in the summer before classes started.

I agree with hyegeek -- being as prepared as possible the night before helps you get going. Another thing I do is set my alarm on my phone and put it in another room with my packed bags. That way, I actually have to get up to turn it off.

I also set up weird incentives for myself like, if I bike in to work I'm allowed a fancy (and fatty) breakfast sandwich. If I don't, then it's yogurt for breakfast. I don't know if that works for everybody but sometimes food is my best incentive!