We have workflows which have vcenter information used for input selection (selecting a VMfolder, or network for example).
When the Orchestrator service restarts all cached vcenter information is lost, consequently when a workflow is run for the first time it takes a period to load this information into cache.
Is there a way of loading this information via a workflow for example?
You can address this with a policy that run a workflow when the server is started.
You can do what Daniel proposed (but it may be a bit overkill if you have a large infra) or load a specific object type using Server.findAllForType() or load specifically the part of the vCenter objects you are likely to use with enumerating the objects of a particular inventory branch.