I can never get myself to start things. When I do, however, and there's an unsolvable problem that needs solving, if I pick up even a little momentum in trying to solve it, I will stay on the task/project like Gorilla Glue on rye. Literally, I will forgo meals and sleep till I can get the problem solved.
I think this mindset is largely why it's hard to get started -- Projects and tasks feel overwhelming, where I unconsciously feel like I'll have to finish it all in one go, even if it takes hours on end. It's hard have momentum and then stop and switch to something else.
How do I better shift "gears" by switching to other tasks/projects that need doing/solving? How do you feel OK about leaving something unfinished for the time being and switching to something else?