This sounds very familiar to me, I guess I'm the same.
Although, once I do get started, I tend to work a bit obsessively
The business partner is a very good idea! I noticed from experience that I stall less when someone is working on the same thing as me, or someone is expecting something from me.
But it's hard to find a good business partner. I can be a bit of a perfectionist sometimes, and not easily satisfied with the work of others. Definitely something to work at!