Strange cold start on 84 4000 quattro

[DK]

I had something similar happening to my 86. The coolant temp sensor
(for the ECU) developed a leak and coolant accumulated slowly at the
connector. Made the readings go haywire. Disconnect it next time it
happens to start troubleshooting. I tightened the sensor mine up and
cleaned the connectors and the problems where gone. My car usually
took around a minute till it acted normal and would fall flat on its
face when you tried to drive it.