I know I do.
One strategy that helps is at the end of every work session jotting down what is the next logical step, the thing you'll do first when you resume.
It's a good idea to do this even when the next step is obvious. I believe your brain keeps working on a project when you think you've stopped. By pointing it in the direction of your next move you'll find when you resume you feel less resistance.
Try this for a week and notice to what extend you're getting more into the flow--to share your experience, please use the comments section.
(You'll find a wealth of useful and innovative approaches to getting more done in my book, Focus: Use the Power of Targeted Thinking to Get More Done, available via any bookseller.)