I'm sure most of us have been through this. It's the classic combination of laziness and procrastination. Well I'm here to tell you that this is a very easy problem to fix.
Before we actually go ahead and remedy the situation, let's look at why we fall into this problem. You see what happens is that your brain looks at any problem as one whole piece. When you look at a problem, you see it as a whole, you don't immediately break it down into smaller tasks. The reason you don't get started on a task is because you look at it and then, on some level, you think to yourself: "Dang! This is a big problem. There's no way I can finish it, so there's no point in starting."
And then you don't. What ends up happening is that you never get around to starting the task until the last minute when it becomes a do or die thing.
Now that you know what causes your laziness, here's how to fix it: say to your self that you will only do this task for 5 minutes. In fact, set your kitchen timer (or you can keep a timer in your office) for five minutes. What this does is that it gives your brain the impression that its only a small, easily accomplishable task that you are tackling, so you are more likely to actually get started.
Once you actually start, more often than not you'll find that its very easy to keep going. I've been using this to get a lot of work done lately - stuff that I would normally put off for "later". So give it a shot and tell me how this work for you.