I don't reboot frequently enough to remember precisely, but I believe when the Finder is first launched it will automatically open a window if none are open already. So if you've closed all the open Finder windows before shutting down, it will open one new one when you restart the computer.
Even if you do reboot frequently (though generally sleeping the machine is almost as good and starts up a lot faster), this seems pretty minor--is there a reason you don't want that happening?
If you're thinking that having multiple Finder windows open will slow things down, that may be a side-effect of switching from Windows; Windows launches a new process for each window, while the MacOS runs all the Finder windows within one "Finder" application. Having several open has little if any noticible effect for the most part. (The downside, of course, is that if the Finder stalls ALL the windows stall.)
Assuming there's some particular spot you always want to get to, you could also do this: Just set that as the "New finder windows open:" in the Finder preferences, so that's what you'll get. Or just leave whatever windows you want open when you restart--it should re-open the same windows after the restart.
