Most of the time spotlight is showing nothing after upgrading to el capitan I use spotlight a lot but after upgrading to el capitan most of the time its showing empty window.

Its very annoying. How can i solve this problem?
I too see this behaviour. Typing an extra letter or even removing a letter from the search term tends to fix the problem.

This appears to be a bug in OS X 10.11. Please can you provide feedback to Apple. Every report helps!