It works fine. Thanks.

That is not to bad. All open tabs are gone but Opera still remembers logins.

There has not been a definitive improvement. So I guess I have to delete all sessions now. This reminds me of an old advise for running a computer: Do not install anything on it.

Virusscan shows nothing.
There are no extensions.
There were many plugins, I have disabeled half of them. Then let's see what happens, before I erase the sessions.

For some time I have experienced that Opera seems to "fall aslep" for a short time then continues as before. Normaly no input is lost but sometimes keyboard input (af few characters) seems to be lost. This is especially irritating when keying data into a form field, but changing "tab" may also be delayed. Watching video and animated GIFs also freeze for a few seconds. Interestingly sound is never impaired.

No other programs suffer and my pc does not seem to be burdened with heavy programs. Right now I have 4 GB free ram and the cpu is at less than 30%. But Opera falls asleep. The disk does not appear overloaded either.

I do not know for sure when this began but it is probably within the last few months.