Server freeze issue

Hello,
When i reset or update to server, the server is freezing for a long time…
This problem is always happening, why?
Thanks.

it could depend on what is running on the server, when the server gets updated/restarted then for a short period of time it will not work, it also depends if it is an upgraded server or not, usually an upgraded server restarts faster

how long is that freezing time? how does it manifest?