Not connecting to Domain

I log in into my domain using my domain ID (e.g. PG13423) and this ID is
associated with my name John Smith.
So when I log successfully in on my start menu I can see my name on the top
of my start menu.
After sometime, I wont see my name but instead I will see my domain ID
(PG13423)
Once this happens I am not able to print to my printer I cannot access my
intranet cannot access network shares.
So then I need to log off and log back on and then only I will be able to
access all the above resources.

Any clue why this might be happening.

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