I don't know if you have already read about this SpaceDinosaur, but I found that understanding the science behind baby sleep helped me understand the bigger picture.
So in the newborn phase, baby sleep is like it was in the womb - passive. As long as all needs are met (primarily hunger, comfort and security) then baby will sleep. Waking happens when a need is unmet and the passive state of being asleep returns as soon as the needs are met again.
Then as baby leaves the newborn phase (ususlly 2-4 months old) sleep matures and instead of being passive, it's an active endeavour. Sleep now exists in cycles. These cycles involve a brief light sleeping phase between deeper sleeping phases.
The light sleeping phase is left over from hunter-gatherer days when humans could be eaten while sleeping. So the brief light sleeping phase is an 'environment check', not meant for properly waking but offering a semi-conscious time to check all is well.
In adults, these light sleeping phases between sleep cycles may involve turning over, pulling the duvet over you, glancing at the clock. But imagine you entered this semi conscious phase and realised instead of being in bed where you went to sleep, you were now in the backseat of a car. You wouldn't just roll over and go back to sleep in that case, you'd probably be fully awake within seconds wondering WTF happened. This is why it's important that baby goes to sleep in the same place they can stay asleep. It's fine if this is in your arms or next to you in bed. It diesnt doesn't have to be a cot. But moving a sleeping baby is never a good idea for long term sleep.
The fact that sleep is now an active endeavour and that baby is sleeping in cycles - it now means that parents have to work to get baby to sleep. Some babies nedd less work, some need more. They all need active help though.
Some things that help:
- something to suck (dummy nipple)
- perpetual movement (Have you tried a bouncy chair?)
- secure feeling (feeling you hand on them, in your arms, swaddle, sling)
- plenty of calories (frequent, big feeds to calorie load in the daytime)
Limiting awake time is really important. Initial tired signs mean baby should have been asleep about half an hour earlier - the idea is to anticipate sleep and have baby asleep before they show any tired signs.
Some people call this stage the 4 month sleep regression it's actuslky actually not a regression, that suggests that it's only temporary and if you keep doing what you are doing you will come out the other side. That isnt true, it's a perminant change to the nature of sleep. It will last as long as it takes for parent and baby to learn a new way to get to sleep. It might take only a few days/weeks to adapt. In some families it takes many, many months and they don't really adapt at all.
I don't know if that's helpful. Or not. It helped me to understand the reasons for seeing what was happening with baby's sleep.