Wandering idle issue

My idle is behaving a little strangely and I’m hoping somebody has some advice before I just head down to the shop to get it looked at.

When I start the car up on cold mornings, the idle is very low, and sometimes I’ll have to give it some gas to keep it running until it warms up a bit. Once it does warm up, the idle starts to do a slow waver (maybe 200 rpm up and down) pretty slowly. I checked vacuum lines, and they all seem like they’re doing fine. Any ideas as to what would cause this strange behaviour?