Ok I've stopped the windows 10 updates, removed all windows programs that are not important and switch off all visual effects. So far 24h of mining with no pause or blocked... If it happens again I guess I have to increase the RAM size...
Is the rig supposed to run without any restart for weeks or is it normal to restart once in a while (how often?)
Windows 10 will restart automatically, randomly, to install security updates if you don't edit the registry.