This used to happen to me until I found why I lack the willpower to start (at least in my case). The tasks were too big. I started using GTD (with a tool called Nirvana) and slicing all my "tasks" into units small enough to be executed in five minutes.

E.g. rather than "Research using Foobar in the next mobile project", the first task is "Write a Foobar Hello World". Rather than "Write proposal for project X", the first task is "Draw logical architecture diagram for X".

I find the inertia against getting started is a lot less when the task is a five-minute, self-contained unit. It also helps task switch because you don't treat them like links in an unbroken chain of tasks, but individual units.

Only downside: you have to spend some work up front slicing your projects into smaller units. It's kind of analogous to story slicing...