DD (almost 5 months) has been making this noise lately. It's like a droning "nnnnnnnnngggg" noise. She does it constantly. It's like a whingy noise and she looks a little unhappy too. It usually starts after she's had a feed and been up for maybe 20-30 mins.
I have a feeling it might be frustration - she's rolling onto her tummy and trying to push her bum up and reaches forward with her hands, so maybe she really wants to be on the move and is frustrated.
She's happy when she's carried or sitting in her high chair watching me.
She has had reflux but that's resolved now and I'm pretty sure the noise isn't because of pain or discomfort.
Anyone else's bub do this? Did you work out what it was?