All the data of symantec are stored in c drive. So it can reflect in critical mode.
Drive is full onle 712 mb space available.
How to free the disk to use the server continue without any problem?
What is exact SEPM version?
See here:
Disk space management for Endpoint Protection Manager
How to free up disk space on a Symantec Endpoint Protection Manager server
Managing log data in the Symantec Endpoint Protection Manager (SEPM)
How many content revisions do you have set ?
See some articles
Clear the data\backup folder
data\client packages or install packages....
This should give you more free space..
If you still have issues, Do a DR and move the SEPM to a different drive.