Baby may be going through a major leap in development known as the wonder weeks. During this period of time which will last for a week or two, babies are known to display the 3 C ( clinginess, crankiness and crying )
A leap in development means suddenly there are so many changes in his head and this change is so great that his world suddenly looks different and is too much for him to cope thus the fussiness.
You can check out https://www.thewonderweeks.com/ they have more information and when these leap happens. They also have an app called the wonder weeks for easier usage.
Reine Tsukino