Key Combination for Restart During Boot
Although Apple publishes a list of OS X keyboard shortcuts for startup, there is not one for forcing a reboot.

However, your problem seems to be indicating a failing hard drive, so make sure that you create a full backup of your data (if you don't have one already) as soon as possible.

I would replace your drive manually (if your Mac has a user-serviceable hard drive) or take your Mac into an Apple Store for service.  In the long term, this should solve your issue.