Out of the blue stiff steering

Brand new here to the forum, but have been a Tundra owner since 2009. I am not mechanic, but wrench from time to time.
I have a 2017 TRD Pro CM with 115,000 miles on it. I took to work (from a 50 degree garage) and noticed just an ever so slight stiffness when I turn and then it eases up and tightened up again. It sat outside in 15-20 degree air for 8’ish hours. I came out from work hours later to leave and noticed the stiffness was much worse. As the truck warmed up, the stiffness became less and less, but still there.

All maintenance has been done at the dealer and every item has been done in time. Yes, I am the original owner. It has never had anything break or even a recall. Just a great truck!
I checked the power steering fluid, which is spot on. The serpentine belt is original, but no cracking whatsoever and checked by the dealer. 5,000 miles ago.

I wouldn’t think the rack would just do that or power steering pump. I was thinking maybe the steering shaft ujoint, but would appreciate some other opinions.
What are your thoughts? I

 

First check fluid, low or old, may need to be added or replaced
Verify pump is working and belt not slipping
Then there is a joint in the steering shaft than can get stiff, bind, etc.

There were some trucks that had issues and either needed that steering shaft replaced or in some cases, the steering rack

Search "stiff steering" here (upper right) and you will get plenty of threads on it.