Thats the explanation the Volvoshop gave me.

Because one morning the engine didn´t start. No ignitation at all. The engine sounded like it was only the starting motor that worked and that the engine was not mowing at all! Very strange sound indeed.

But at the Volvoshop they said that both the starting motor and the engine itself rotated and was OK, but that the oil looked strange. Like glue.

They just let the starting motor go for 30-40 sec and than suddenly it started.

It has never happen before or since.

A reflection I made was that the car that night was parked on a sloping street (with the front pointing up the street). A silly reflection, but, well, you never know these days with the car geting more and more complicated.

The oil, that is important of course, was quite new, approx 4 month and 5000 km.
Syntetic and not a cheap type.