There is no Esri-recommended order in which the Enterprise components should be stopped/started. However, Portal by far has the longest startup time. With that in mind, I usually restart the services in this order:
FWIW, I've been taught by some Esri folks that a preferred way is to stop and start in this order.
Data Store, ArcGIS Server, Portal.
The unintuitive thing is to bring them in the same order that you stopped them.
First Data Store, then Server, now wait a few minutes then bring Portal. Give Portal about 5 minutes to settle in.
Apparently Portal prefers to find the services already up and running when it comes up.