I have a 2001 Nissan Frontier, 5 sp auto trans, 3.0 ltr v-6. In cold weather I have to drive 6-7 miles at highway speed (55-60 mph) before it will shift into overdrive gear. Is there a temp sensor that requires warm-up before it will shift. After it warms up it works just fine and in Summer months no problems.
There are various temp sensors - I don’t know exactly what your transmission uses - might be the coolant temp sensor or maybe a transmission fluid temp sensor. But either way this kind of thing is perfectly normal.
The only thing I’d suggest is to check your thermostat. If it is sticking open it will take longer than it should for the car to come fully up to temperature.
It sounds normal compared to some of the autos I’ve had. The only way it would be a concern is if it’s now behaving differently then before. Not knowing how long you’ve had the truck, only you can determine that.