Oscar1976,  The error you are seeing (2900:0221) is referencing something existing in the hardware log of the iDrac. It normally is a reference to an error in the past. If you access the iDrac web interface and go to hardware logs, you can verify if this happened previously. Normally the error return for an issue that is currently happening will start with 4400:. When does it show this error occurring? Also, If you clear the hardware log 32bit diags won't report that error.  With what you are describing it sounds like an OS issue, but I would suggest making sure that the server is up to date on BIOS, iDrac, and Raid Controller.  As those being excessively out of date can causes issues like this as well.  Would you also confirm what controller is installed, as well as where those devices versions are currently? Also, in the OS could you go to System - Advanced Settings - Startup and Recovery and then verify that the is NOT a checkmark in the Automatically Restart box. This is to see if there is a STOP code that occurs before the shutdown Let me know what you see.  
I have a T410 that shuts off after about 30 seconds with no errors or warnings,  When I ran the Hardware Diags, the system failed with a failure code of: Error Code IPMI 2900:0221, MSG, System Board:: Voltage Sensor (5V PC) State Asserted "System Board".  I am not able to stay logged onto the server in normal mode but can keep the server running in Safe Mode.  I was not able to locate any errors in the Windows logs that indicate anything amiss in the OS,  By the time the remote location notified us that they were experiencing issues with this unit constantly rebooting the RAID has experienced massive disk corruption which I was able to correct with Disk Check.  The server will boot with no errors or messages and then just power off after about 30 seconds with no warning.  Can this component be replaced and is so then what would be the part #,  Since this is out of warranty I am looking for any assistance possible to repair this issue as this is still a good server that just happened to fail following the warranty expiration.  Thank you
T410 Voltage Sensor fail