2012 MB Air | Rapid 10 second screen flicker after wake from sleep.

This morning noticed a very rapid flickering after opening the lid. I can recreate it by  Menu> Sleep or closing/opening lid. It lasts about 5-10 seconds then fades and is no longer detectable.

I have reset SMC/NVRAM and booted into Safe Mode and rebooted. Extensive diagnostics tool reported nothing. Flicker is most apparent on a grey image.

Specs:

MacBook Air (11-inch, Mid 2012)

Yosemite 10.10.2

Intel HD Graphics 4000 1024 MB

My question is whether this is indicative of hardware beginning to fail or normal for age/specs of Apple display. I don't recall ever seeing this, but I had a grey image on my screen when I opened the lid and noted the flickering today.