Holding a sleeping baby is very calming, but after a while you really like to do things by yourself, like going to the toilet...
My mum send me a book called baby-gami (link), a very funny book about wrapping up a baby like the little present that they are, wow does it work! The whole startling (moro) reflex keeps waking them up, making them cranky and tired. All wrapped up they sleep for hours, warm, safe and content.
Alex also sleeps so much better when wrapped, I use a thin muslin wrap on warmer days.
5 weeks and so tall, he won't be able to use his bed for much longer!
The basic technique,
I tend to tuck their hands under the small triangle in step 2, making it escapee proof.