That's basically just Sync updating itself,similar to (maintenance mode) with the black screen thats lasts for a few min and no need for alarm unless there are DTC set.
There is a TSB,SSM on the APIM interface module protocol. Z
TSB #SSM-45809
NHTSA ID #10078984
Date Announced:
MAY 09 2016
Additional Info:
How to Fix
Summary: SYNC 3 ACCESSORY PROTOCOL INTERFACE MODULE (APIM) DTCS U3000 OR B108E OR U1A00