my starter has twice now not seemingly been geared to the engine... whining sound of it spinning freely. It's been very cold and I've backed into parking areas and shut down car only to have problems later.. I've physically rocked the car in gear and then the starter has decided to engage.. I now dread today's departure from the train station parking lot. Any ideas how to solve this?

I agree with Rule....the starter is the problem.
Mine (85 DL, 209k) does this also but only when cold. It usually only does it once and then it will crank up. I bought that starter at a pick and pull because it looked like it was rebuilt and mine was original. I'll bet that it was taken out and replaced for this problem but was not diagnosed properly when it was rebuilt.

I think it has to do with the solenoid that pushes the bendix (gear) out and engages into the flywheel. The solenoid seems weak. When the solenoid pushes the bendix out it makes a contact to send voltage to the motor.

Replace the starter

do NOT replace the starter....I have experienced the same issue several times on several cars....the issue was correctly spotted before...it is the selenoid. if the whirring is being heard, well then obviously the starter is spinning!...the prob is that the selenoid is not thrusting the gear on the starter out to meet the fly wheel and is freely spinning....a complete starter and selenoid package will solve the problem but is unnecessary and probably more expensive than the selenoid alone. my last starter was $80 remanufactured and my last selenoid was $15 new. when u do this stuff remember 3 things. 1) disconnect the battery so that you don't accidentally short and spark/weld anything 2) shimms may be involved to align the parts properly as to allow the starter gear to mate with the flywheel's teeth 3) starters are way way heavier than one my think....(the one on my 6.6 liter pontiac nearly smashed my face as I was expecting 5 lbs or so and it was really more like 30lbs....so use more than 3 fingers to hold this sucker up even though the brick cranker is prolly more like 20 lbs) good luck

thank you all for the rapid feedback....