Hi,
From your description, I understand that your Windows Server 2003 often freezes and you need to manually restart the machine.
Based on this situation, please first try clean boot to disable third party service and application to monitor if the issue can be fixed.
1. Click "Start", go to "Run", and type "msconfig" in the open box to start the System Configuration Utility.
2. Click the "Services" tab, check the "Hide All Microsoft Services" box and click Disable All (if it is not gray).
3. Click the "Startup" tab, click "Disable All" and click "OK".
4. Restart your computer. When the "System Configuration Utility" window appears, please check the box and click "OK".
Meanwhile, you may open Event Viewer to check if there is any related error.
Regards,
Bruce