92 240SE Estate starting problem

I hope someone can give me some clues as to what might be causing an
intermittent starting problem with my 92 240SE estate (auto).

Sometimes it starts normally, first turn of the key with no problems.
However, on other occasions trying to get it started is a nightmare. The
engine will just turn and turn without showing any sign of firing.
Jiggling the auto selector and pumping the throttle seem to make little
difference until the engine suddenly catches and starts.

The implication is that there is no fuel getting to the cylinders for
some reason on certain occasions. Temperature makes little difference
nor does the fact that it is the first start of the day or a start-up
after being parked for a few minutes. It can start normally at beginning
of the day and then be awkward next time I try it after being parked and
vice-versa

Andy in Huddersfield