Have you figured out the end of the book yet? If you know why he STOPS running, it might give you some ideas about why he started. Or if the character has a sidekick or confidante or at least a secondary character who's on his side, presumably someone who is NOT running, but is very tied to a given location, and you know why he/she has ties, then you can come up with parallel or mirroring reasons for the protagonist to be footloose. Or perhaps the very reason that one character is tied to a location is the sort of thing that would, in the other character's personality, cause him to avoid ties.
Another option: give yourself fifteen minutes to write down all the possibilities you can think of, regardless of how silly they seem. You've got the first handful already. Make yourself keep going, at least to a dozen, maybe 15 or 20. Don't stop and think, just write them as fast as you can. Then take a break, go away and forget about it for a bit. When you come back to the list, the first few will be cliche, and a few will be totally insane, but somewhere in there, you'll find something interesting that can work, although it might need some tweaking.
You might want to do this exercise long-hand, not on a computer. There's some theory out there that writing with pen & paper calls on different, potentially more creative, parts of the brain.
JD
