Transmission acting weird. help!

I have a 1991 Mitsubishi Eclipse and i am having a lot of transmission trouble. When i first start it, cold, i will put it in reverse and it will jerk back hard. then when i put it in drive and push on the gas, it acts like it is not catching and will rev. If i put it in Low gear, it will work. or if i push on the gas and the brake and then let go of the brake it will go. It will be fine after running awhile. Once it is warm, the transmission runs great. Not sure where to go from here. Some people say to change the tranny fluid and filter but some say that does nothing. Its an automatic also, but if anybody could help that would be great. thanks

I'd do the fluid route first (cheap and good practice) then look to possible TCU issues, and lastly internal trans issues.

ok cool thanks i will try that

Yeah I'd start by changing the fluid, but make sure you change the filter also. See what that does, then go from there.