The symptoms for this problem are that Windows 10 suddenly freezes shortly after logging in. The screen stops updating, the mouse and keyboard are unresponsive. The particular PC seen with this was a Toshiba Satellite C70-A with Pentium Processor. When restarted in Safe Mode the machine ran and repsonded normally. The issue was caused on this particular machine by McAfee LiveUpdate Anti Virus. By uninstalling the McAfee software in Safe Mode and restarting everything was back to normal. On this this machine the McAfee subscription had already expired.
If you suspect this may be a problem and you have enough time to start the task manager [CTRL+SHIFT+ESC] look for a McAfee Scanner service taking a high percentage of your CPU time!