My (07, electric) tachometer's been sticking on a cold start recently. I've checked the wires and the connections seem tight without any real noticeable corrosion.

Suspect it's actually seizing up a bit internally, and needs a bit of voltage from the engine to unstick. Anyone else had this issue? Guess I can just disassemble this and lubricate it up, or?

Mine has been doing that too, for the past year or so... but mine's a '98. I just tap it a bit with one of my knuckles and the needle frees up... but it would be nice to fix it.

Interested to see what replies you get!

I haven't pulled one of these down, but done a few similar speedos. (This applies to cable driven Tachos and speedo, but electronic ones might be different).
Getting the the rim off without damaging it is the hardest bit - in the past I've ground a slight curve into a woodchisel tip to help the rim off. But doing it without cracking the shell is the problem.
I've found that washing the mechanism out with meths or similar solvent frees it up. The mechanism will be a magnet connected to the cable drive, that spins, and the needle is connected to a steel piece which is 'attracted' by the magnet, and so spins up with it.