All you can lose: the problem that stops Explorer behaving as it does now. It's not sure it helps, but it won't harm. If you don't know how to start System Restore, better google that first.
However, it's not really clear what happens. After all, the first thing you see of Explorer is the desktop. If you see the desktop and it's stable, Explorer is not restarting. And that makes me wonder under what conditions it restarts every second and what happens then. After an hour you would have 3600 Explorers open, and that seems enough to totally stop Windows.
Moreover, since theme settings are user dependent, does this happen only in one Windows account, or does it happen in all Windows accounts you login to?