I'm new to the group - desperately need advice.

I have a 97 Prelude (Automatic/Tiptronic) - over the past 2 months on a cold start when putting my car into first gear something sticks & the car shudders forward (almost like popping the clutch on a standard), it does this between first & second & revs pretty high then it sudders forward again, something keeps sticking & the car hesitates between gears - it's pretty bad & it's getting progressively worse.

It only does this during the first 5 min. of driving & on a cold start, once the car is warmed up it runs great. The transmission fluid is turning brown as opposed to that pinkish color it should be - can anyone offer me advice as to what the problem may be.

I'm trying to get a second opinion before forking out large cash to replace the transmission if in fact that's the problem. What if I had a transmission flush or tune up, would that make a difference? Could it be the choke????

Bare with me, I know nothing about cars. Thanks!