"Seasonal" Starting Problems

Need some help diagnosing this.... only a few times a year, round abouts the change of the seasons (happened again this am, WARM in Virginia) when weather seems to fluctuate drastically, our '99 Volvo V70 w/ 85k miles has this starting problem:

When turning the ignition key, it cranks fine but just doesn't catch. It seems to want to "try" but gets the feeling of flooding out - even without touching the gas pedal even once in the beginning. The only thing that seems to finally start it is to keep cranking the ignition with foot floored on the gas pedal, sometimes playing it up and down a bit. Finally it sort of catches, bogs and sputters (with pedal still requiring to be floored and cranking) and then comes to life. Will also start fine if I wait 20 minutes and then try again. Next time I start it it's fine. Does it yearly regardless of all regular maintenance.

Any ideas on this?

Thanks.

Volvos in those years with drive-by-wire had trouble with the pedal servo assembly. Sometimes the position of your right foot doesn't correspond to the position of the throttle. If the throttle is in the wrong spot during cranking it might be causing the problem.

I would also check the coolant temp sensor. If its giving the computer false readings it might not be giving it the right startup mixture.