I have been noticing this problem for a few years in my 2006 s-type. The first time I open a door in the morning, I am met with strong smell of what I believe is ethanol. After a few minutes of driving the smell completely goes away. Recently, I replaced the cabin air filter and i thought i solved the problem. But within a few months, the problem returned. Despite the ethanol smell, I have never noted the smell of gasoline in the cabin. Perhaps this is because ethanol is more volatile.
I believe the smell is starting in the engine compartment and is drawn into the cabin.
It has never been clear to how the system works that is supposed to circulate vapors from the fuel tank but i suspect that is the source of the problem. I have no trouble codes and the associated monitor, although it takes a long time to reset, does so eventually.