That means there's an error somewhere.
Power shut it down then boot up into the Advanced Boot options - this can vary depending upon Windows version and make & model of computer, but it's usually done by tapping F8 as you switch on.
Select Repair your Computer and navigate to the Recovery Environment to select Startup Repair and you can run this up to three times if at first it doesn't resolve.
As it's continually rebooting in Safe Mode, it will be difficult to run the WR program again to restore the registry, so hopefully Startup Repair will do it.
There are Bootrec commands you could try if Startup Repair doesn't fix it, but you need an install disk to boot up with to execute those commands.