It is just intermittent fussing.... while sleeping. And as a baby gets settled.
It does not mean he is 'awake.' He is not.
Even adults, make noise in their sleep.
Babies do that too.
Even older kids do that.
If he is not 'waking' waking...then you can leave him be.
Its fine.
BOTH my kids as babies did that too.
Its okay.
He is not 'crying'... just fussing or making intermittent sleep noises and as he self -soothes.
But, if/when he DOES wake and then cries... THAT is when you go and feed/nurse him.
You will get used to his noises and what it means... and then once you get to know his cues... then you will feel better.
He is ONLY 6 weeks old. And yes, you need to feed/nurse on-demand... when he wakes wakes up.
Next, it is also the parents that can sometimes wake a baby... snoring... can really wake a baby too.
There is no need to cry it out. He is not a problem...and he is merely being a baby.... they do this, they make noises in their sleep too... but when he IS hungry and needs a feeding/nursing...you will know that.
My kids are 4 and 7 years old. THEY make noises during their sleep too. It doesn't mean anything, it doesn't mean I wake them up, it doesn't mean I have to make them cry... it just is. Some kids or babies.. make noises in their sleep. Its okay.
Even some adults are real noisy as they sleep.
Next, sleep is NEVER static... in a baby or a child. It does change... right now and later, sleep 'patterns' changes. It is normal. And each day or night, appetite changes too... and at growth-spurts... intake and hunger in a baby changes. So, that is why, you need to feed ON-demand... never by a schedule. You will know, your baby..... when your baby is hungry. By his cues.
In an infant, growth-spurts are every 3 weeks. Then at 3 months old, 6 months old, 9 months old, and every 3 months.... at growth-spurts, a baby gets way hungrier and feeds more frequently and needs more intake so that their intake keeps pace with them and that your milk supply... increases as well to keep up with your baby, too.
all the best,
Susan