My almost 4 month old will coo and grunt when trying to fall back asleep, sometimes a winge (not cry). If he doesn't fall asleep and cries loud and upset, I pick him up. That's the method that works us.
Ps. My DS1 was formula fed and woke 2-3 hrs at night for a feed, my DS2 sleeps through the night, so all babies are different in that regard.