Try resetting NVRAM/PRAM http://support.apple.com/kb/ht1379
if it where me I would take it into have checked out. In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test
At the least it will establish a "service record" for your issue on that machine; and may benefit you down stream if it fails out of warranty.
Make an appointment
https://www.aphttps://support.apple.com
https://checkcoverage.apple.com/
https://support.apple.com/my-support
https://support.apple.com/en-lamr/aasp-program
From iOS online Genius Bar appointment:
https://itunes.apple.com/us/app/apple-support/id1130498044?mt=8