If I'm using a sleeping bag with a nylon inner surface then either very thin pajamas or a very thin fabric liner can reduce that clammy/sticky feeling. I've never bought a sleeping bag liner. I simply made one from a thin cotton sheet. I just slip it into the sleeping bag and don't try to fasten it to the interior of the bag.

A sleeping bag liner also helps a lot to keep the sleeping bag itself clean on the inside.

Having pajamas like others suggest can also give you that extra layer of clothing if you need it.

I like to have as much of my stuff do double duty as i can.

Cheers