Mine bark now n then, usually around 2am as well lol. If I hear it ( I usually do ) I get up and talk to them, put my hand in the cage, give them a pine nut and go back to bed once they have settle in again.. I always just figure they are wondering where I am or where the other glider is if one is in the pouch and the other is out.
I would guess they stop barking because of the light you turn on. It's probably to bright for them and an abrupt change from the darkness. Maybe try using a flash light or cell phone light (indirect light ) to see which one it is and let them know you are there instead of the regular light.
As far as mine are concerned I haven't noticed them barking more because of me getting up to say "hi, I'm still here " They spend the majority of the day
on me, so if they are barking
for me I take it as I am part of their colony and they want to know where I'm at. I don't think it's about attention, I don't usually stay up long when they bark, just long enough to settle them. Of course then there are those nights I can't get back to sleep n think well I'l get back up and go play with them, only to find they have gone in the pouch for a nap lol