my car runs pretty different when its cold then after its warmed up. what sensors only turn on after the car is warmed up?

1994 325is OBD1

The only sensor that I know of that is ignored on a cold engine is the pre-cat O2 sensor. Until the engine has warmed up the DME is running in open loop mode using data from the MAF and timing reference sensor. Once the O2 sensor has reached operating temperature the DME will enter closed loop mode, adjusting the mixture according to feedback from the O2 sensor.

The other difference in cold vs hot operation is that the DME will command a richer mixture on a cold engine. Essentially an electronic choke. A minor intake leak or contaminated MAF can have a larger affect on hot engine idle since the mixture won't be enriched.

FYI: Useful life of a pre-cat O2 sensor is not more than 100k. And by 80k most have aged enough to justify replacement.