If you have booting problems even in Safe Mode, you may need to repair your Windows startup by using the Windows installation drive. Boot from it and select the Repair option. It should fix some system errors without harming your data. Once the process is completed, restart the PC and try to boot normally. If the same issue appears, you may need to reinstall the OS. Have in mind that all data stored on the primary partition will be deleted and you may need to back it up.