Transman what do you think?

I have a 1997 Nissan truck, with a 5-speed manual trans. It has 126K miles. Especially when it’s cold outside, I can’t shift from 1st to 2nd, or do so with difficulty. All other gears are OK. I have to shift from 1st to 3rd and then after the truck warms up I can shift to 2nd. I’ve already replaced the gear oil in the transmission and have checked the hydraulic clutch fluid. What’s the problem?

Outside temperature? Most five speeds will do this at some point.