A few general thoughts:
You may need to further break down those tasks which you keep putting aside. Make the next action a more palatable bite, and it will be easier to take that first step. Once you get some forward motion, continuing is usually easier. Reluctance to tackle that first next action could be an indication that you haven't really figured out what it is you need to do.
Another source of stuck projects is lack of commitment. Maybe you aren't tackling any of those next actions because you aren't really committed to the project. Re-evaluate whether the project is something important to you, and put it on hold or drop it if you aren't committed to getting it done. Be ruthless! You can waste a lot of energy looking down lists of actions and projects you aren't going to do, so don't do that. You can always bring them back from the deep-freeze later if needed.
If your lists are stocked only with actions on which you can make immediate progress, and to which you are committed, moving forward should be easier. Open OmniFocus, bring up a Next Action view for the available context(s), take the top action on the list, and do it. Repeat until the list is empty.
Another tactic that may be of some use is to combine reviewing and doing. If you've got all of your next actions down to reasonably small chunks, try doing the first next action on each project as you review it (within the limits of possibility, of course). Use OmniFocus' splendid review feature to keep track of what has been reviewed, and set the review intervals according to how often the project needs to be bumped along. If you can force yourself to do just one action each time you review a project, setting the review interval on that project to 1 day will get you steady progress. If, on the other hand, you find that at the end of the day, you've only gotten through the 1 action for a handful of projects and have barely started to scratch the surface, that might be a good indication that either you are overcommitted, or your next actions are too large for this style of working, or perhaps both. If you decide this might be a workable approach, and you have more than a couple of dozen projects, you might want to investigate my suggestions on review spacing, which can be found by searching for "prime number review".
Sometimes just bringing up a list of tasks sorted by duration and tackling a handful of the shortest ones is a good way to get moving, too. Sometimes the satisfaction of checking things off as complete isn't enough to overcome inertia, but it is enough to keep you going once you've gotten started. Make it easy to get started!