In order to troubleshoot the issue better, please provide more information.
Are you getting any error message at the time of booting the computer in Safe Mode?
Are you able to boot to the desktop in normal mode?
I would suggest you to perform Startup Repair and check if the issue is resolved.
Startup Repair is a Windows recovery tool that can fix certain system problems that might prevent Windows from starting. Startup Repair scans your computer for the problem and then tries to fix it so your computer can start correctly.
Startup Repair is one of the recovery tools in the System Recovery Options menu. This set of tools is located on your computer's hard disk and on the Windows installation disc.
1. Remove all floppy disks, CDs, and DVDs from your computer, and then restart your computer using the computer's power button.
2. Do one of the following:
o If your computer has a single operating system installed, press and hold the F8 key as your computer restarts. You need to press F8 before the Windows logo appears. If the Windows logo appears, you need to try again by waiting until the Windows logon prompt appears, and then shutting down and restarting your computer.
o If your computer has more than one operating system, use the arrow keys to highlight the operating system you want to repair, and then press and hold F8.
3. On the Advanced Boot Options screen, use the arrow keys to highlight Repair your computer, and then press Enter. (If Repair your computer isn't listed as an option, then your computer doesn't include preinstalled recovery options, or your network administrator has turned them off.)
4. Select a keyboard layout, and then click Next.
5. On the System Recovery Options menu, click a tool to open it.
Another option is boot in safe mode with command prompt - type: sfc /scannow System File Checker
