How to do when your 4 months child is crying?

I'm not a parent but I have been a nanny and a teacher, so I do work with children a lot. My best advice is to just check the basics first (are they hungry, need a diaper change, etc.) Some small babies are colicky, which causes them to cry a lot. Another huge trigger for those tears is gas. Babies get very fussy when they're gassy. Maybe rubbing their tummy would help soothe them? If the baby is crying a lot and you don't know why, you may want to visit your doctor and just make sure baby is ok! Hope this helps. :-)