My transmission won’t kick in to gear until the engine is warmed uP? Why is that?
This is usually a sign of low fluid level. Is the transmission fluid level up to the full line with the transmission warmed up; engine running in ‘park’ and on a level surface?
If the fluid level is okey, you might have a problem with a lazy seal on one of the clutch pistons. The seal will work as heat gives it more flexibility.
You might be able to help us help you by providing the make and model of the car, the mileage, whether this is an automatic or manual, and whether the fluid has been serviced regularily.
Is this an automatic transmission? You didn’t say. If so, have you checked the transmission fluid level?
If it’s not low on fluid, you need to tell us more than the year of your transmission. Lots more.
How about giving us some more information. Need to know Year, Make, model engine size. 2 or 4 wheel drive (where applicable). When was the last time it was serviced??
Your problem could be almost anything because different transmissions have their own little quirks.