I am running a dual boot Ubuntu/Windows 10 on a Lenovo t460p. In order to resolve hdd issues between the operating systems I disabled hibernate in Windows:
powercfg /h off
Since I did this change (confirmed as when I enable hibernate, all works as expected), Windows doesn't shutdown anymore, but always restarts when I hit the shutdown button. It is the second clean install I did and the issue is definitely caused by switching off hibernate. I can't find any restart problems that are related to fast startup settings and hope somebody can point in the right direction.