you can try restarting your PC and pressing F8 before Windows loads, then choose Start Windows Normally.
If it keeps happening, check for loose cables, remove any new hardware, or run Startup Repair from a Windows installation USB/DVD.
You will need to once again boot your PC but now press F8 or Shift + F8 in order to input advanced options. Choose either Start windows normally, or Startup repair. Just do a system restore or faulty drivers in the event that the problem persists.