Tachometer and Speedometer fluctuate after cold start

Not sure what to call this phenomenon, so let me know and I'll edit accordingly.
On "cold" mornings (South Florida, so like 45 degrees), after getting to mid speed in 2nd gear my meters start fluctuating between zero and the correct reading. This continues until I shift to neutral and back to 2nd (it only happens once in the included video, but I've never seen this).
It's inconsistent, so I finally got a video after trying every morning this week.
Idle is normal, tachometer doesn't twitch, and there's no issues outside of this.

 

Get something like a Scangauge II. It reads from the trucks computer. If the SG does not fluctuate the issue(s) potentially in the instrument cluster electrical or mechanical.

 

Is it bad that I first read this post as “tacometer” thinking it was something silly lol. This site does things to you man I swear.

 

If I just need to read the OBD2 port, I think I have a buddy with one or I can go with some cheaper options.

I understand lol, I thought the same thing typing it. "A meter on your taco? Which one?!?!"