If I run freecad, then select File>Exit or hit the x in the upper right corner, it shuts down the restarts.
If I, after it restarts, I select Exit or X, it shuts down normally.
I did some searching with terms like restart, but, didn't see anything.
No big deal...just makes getting to the first beer at the end of the day take a few seconds longer.
OS: Ubuntu 18.04.2 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.15860 (Git)
Build type: Release
Python version: 2.7.15rc1
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)