Okay,

I lived with a similar problem for a few months and discovered that the fault codes couldn't necessarily be trusted if there was a bad electrical connection. I spent a lot of time replacing components and trying to locate the specific source of the problem - with the help of an experienced Volvo mechanic.

In the end, it was the man connection to my electronic ignition coil that was at fault. The plug went on fine but seemed a little spongy. I discovered that a good hard squeeze made it click on a little further. My car has started fine ever since.

A simple crack or a bad connection in a main lead can lead to what you are describing. Jarring and thermal expansion/contraction creates the intermittent problem.

Good luck - these can be fun to try to find.