Hi Olivier,
Thank you for the update and apologies for late response.
I would suggest you to disconnect all the external devices (printers, scanner, USB (universal serial bus) drives, etc...) except mouse and the keyboard and check if the issue persists.
If the issue does not occur with the external device connected then, try connecting one device at a time to check which hardware causing the issue. If you come to know the hardware device which is causing the issue then try updating the drivers for
the hardware device and check if that helps.
Method 1: Let’s run the performance troubleshooter and check if that helps.
Open the Performance troubleshooter
Method 2: If the issue persists then, run the fixit provided in the following link and check if that helps.
Fix Windows system performance problems on slow Windows computers
Method 3: I would suggest you to perform SFC scan and check if it the issue persists. To do so, please refer the following article.
The SFC /scannow command scans all protected system files and replaces incorrect versions with correct Microsoft versions. For more information how to do SFC/ scan, please follow this link:
http://support.microsoft.com/kb/929833
Refer the following link to update drivers for hardware which is causing the issue.
Update a driver for hardware that isn't working properly
Hope the suggestions help.