How do I develop a routine nap schedule for my 4mo?

Most babies, at this age, can’t be on a strict schedule because many babies are still taking shorter naps while their brain matures and they simply can not stay up very long to get to the next scheduled nap-time, so at this age, it’s likely naps are still on the short side, but come frequently and every day will still likely be different. Don’t worry, that will change! Most babies can get down to just 3 naps around 6 months or 7 months.