After a scan I put all programs in sleep mode. To my great surprise, my MS Office 2019 would not start. I had to run the online repair program and Office started normally, I few days later, the same problem. Since only MS software was affected, I removed both Ms Office 2019 and MS Share Point Designer 2010 from sleep mode. After a reboot, Office started up normally and has done so until now.
Obviously it is MS Share Point designer having caused this problem.