Discovery 1998 Won't go, won't shift

[landilover]

Hello,
My discovery has started shifting strangely, recently when I start out it takes about 5 minutes of driving before it will shift into 2nd, once it is in 2nd, it shifts to 3rd and 4th fine. Usually I drive around at under 30 MPH until it is willing to shift. More recently it has also started no wanting to go into gear at all after I have started it, it starts wonderful, then I move the shifter and nothing happens, just stays in neutral. A few days ago, it was taking about 15 seconds to a minute to go into gear, yesterday it took 15 minutes. I took it to an auto shop a month ago, they kept it 4 days an the only thing they can come up with is they think it is the throttle positioning sensor. Where is this? Does it maybe need to be cleaned? Any advice is welcome.
Thank You.

[JCardoza]

Mine is doing the same thing. Won't shift out of first until the transmission warmed up. Were you able to find a solution? Someone suggested changing the transmission fluid and filter.