For the last week my tach wont work first thing in the AM. After about five minutes of driving the needle will start to creep up and then it will work fine after that. Sure, it's been cool these mornings but not THAT cold. What the heck could be wrong with it?
It still runs fine, so it must just be the gauge?

Connections might be loose.

What brand is it? Usually Autometer is good about working with you on troubleshooting. Unless you are talking about the stock tach. I had problems with that on my GST. It never bothered me so I didn't do anything about it.

It is the stock tach in the dash. I guess as long as everything seems to run fine
I won't worry about it. And so far it has always started working within the first few miles.

I only noticed mine doing it when it was especially cold in the morning. It really isn't that cold right now but, maybe yours is more sensitive than mine was. Who knows.