PBIRS API call is slow on Server

Not sure about a 5 minute delay, but a few things to check:

1. Is the server in a cold state? Sometimes the first call takes time to load everything into memory. 

2. When you view this in the web portal, is does not pull all items at one time, it filters the list to the just that folder/root being viewed. Hence consider if you re rest call shoud have some filter condition. 

3. Do you have large files? Double check the REST api repsonse if that includes the content payloads. The portal pulls only metadata and not the content. 

4. Look at the server log files, that may give you some indication of where time is spent, or if there is a timeout/error of some sort.