Every time I start my server it makes my steam client go into offline mode

[ImKevinTbh]

it does this every time without fail, and when I restart my main steam client it forces me to sign back into my profile

[mr-guard]

Unfortunately that seems to be a limitation of steamcmd as it uses the steamclient.

Can you try to use steamcmd manually and check if the issue persists?

[ImKevinTbh]

It doesn't happen when I use steamcmd normally, it also doesn't seem to happen when I turn off update checking altogether

[AvianoDesigns]

Perhaps during the setup process, you've input your own steam username and password for the account to start the server? If that is the case, you must create a second steam account and purchase dayz with that account and use that account for the server. You cannot use your own account, otherwise while the server is running, your steam account is unusable.