Thanks Zargg and scook. I did it but that's not it. Perhaps the last Windows 10 updates :(.
I tried with my old X2 and X1 and same thing. If anyone has ideas about this issue, I take them :) ?
I have graphical glitches during the launch but again, once launched, it's ok. I analysed my HDDs and no problem reported.
I tried safe mode but no clue either. Sonar itself lauches pretty quickly and I noticed that a project with only audio takes less time to load but as creating a new project takes a long time too (and in X2/X1), it's still a mystery.
I tried with Sonar 8.5 Producer and it's ok.