A trusted Norwegian Volvo mechanic told me this symptom is due to porous fuel deposits in the intake ports near the valves, and on the back of the intake valves themselves.

These deposits "dry out" overnight, then "soak up" a good bit of the incoming fuel on the day's first start. This means the cylinders don't get the fuel needed for much more than idling (maybe poorly).

After a minute or two the deposits become saturated, letting ALL the incoming charge get to the cylinders, and it runs OK till the next lenghty shutdown period. (How long is "lengthy"? I can't say. Maybe just 2 or 3 hours?)

The fix is to run a good quality fuel system cleaner thru. Probably more than just one application. I think these cleaners are discussed in the 700/900 FAQ feature. I'm told they are most effective with a lot of short trip driving, giving the stuff more chances to "sit and soak" -- as opposed to running it thru on a long trip.
--
Bruce Young,
940-NA (current)
'80 GLE V8 (Now gone)
'83 Turbo 245
'73 142 (98K)
'71 144 (track modified--and going to be crushed unless...)
New 144 from '67 to '78
Used '62 122 from '63 to '67