You may have enough miles on the engine that it's a bit tired and can no longer, when cold, produce the torque required at the low RPM required to be in OD.
Or the OD lockup clutch is worn enough that it is simply slipping a bit until the ATF/transmission warms. Checked the ATF condition lately?
nop! my prestone and my tranny oil are the only fluids i didnt have time to change. I'll do that as soon as possible then!
Do you recommend a certain ATF oil?
thank you!
Frank