this sounds a lot to me like an old thermostat is sticking shut.
My truck does this too, it is a 94 but same truck as the original poster.
I am not that concerned (b/c i know to watch my temp gauge) but when i flush my coolant next time I am going to replace the thermostat.
My understanding is that this a very common condition (at least here in our cold climate). The vehicle starts cold and the thermostat is closed, but once the engine coolant hits 190 F (180 F for the v6) the t-stat should open immediately, but sometimes it takes a bit longer due to sticking shut, so the engine coolant gets hotter than normal and the temp gauge head towards the red. Then a minute or two later (in my case) the temp gauge drops b/c the thermostat has finally opened, and from then on no problems.
I would watch your temp gauge and make sure it doesn't hit the red for too long before dropping and you are probably fine. I've only hit the red once but I stopped the truck when i saw it and waited for it to drop before driving again.
I am 90% sure that this is a t-stat problem...could be the temperature sender but doesn't seem to fit the symptoms.
This also happens in my truck during the summer time, i don't think it's unique to cold weather, and it doesn't happen everytime, sometimes the t-stat doesn't stick and sometimes it does.
Flush your coolant if you haven't in 2 or 3 years and replace the thermostat.
i'm almost willing to guarantee that this will fix the problem.