Finder / spotlight / mail search not working For the second time in a relatively short period I am having issues with the search function on my macbook. 

Whether in spotlight, Mail app, or Finder search results return nothing. If I reboot the search works fine again. Unfortunately this now seems to be a recurring problem. 
It's also a recent problem that I never had before, first noted it a few weeks ago. 

Macbook on macOS Sierra 10.12.3.

Any one has this experience? What could it be? How can I prevent it or fix it, without having to restart everytime? 

-- edit --

Following the feedback in the comments, I ran Disk Utility. Disk utility indicates there are errors but doesn't seem to repair them. Final message in DU: 
"file system check exit code is 8"
I have already tried to reindex Spotlight, that didn't solve the problem.
I can also confirm that if you run out of disk space Apple Mail spotlight can become unusable.  My solution is slightly left field but has the advantage of being utterly reliable - rather than trying to rebuild OSX spotlight or force mail to reindex mail, I instead archive mail into EagleFiler (https://c-command.com/eaglefiler/).  EagleFiler maintains its own separate search index so is unaffected by system spotlight issues which I find difficult and time consuming to resolve.   Double clicking a mail message in EagleFiler will open it (and any attachments) in Mail.