Your baby may be sick. Check to see if he is flushed or has a fever. Your baby may be tired, especially after a lot of stimulation. If your baby is too hot or too cold, he will be uncomfortable and will cry to let you know. Some babies seem to need to cry and fuss before they fall asleep.
Some babies are simply more irritable than other babies.
They tend to be fussy and tense. This is their normal behavior. If your baby is generally irritable, try to keep in mind that he won't always be that way. It can be very stressful and upsetting to a parent whose baby cries a lot. Try to remember that young babies cry because they are expressing some need, like hunger, that must be met.