Error message on console - Out Of Memory

We recently installed a fresh install of server 2012, SQL Express 2014 and Solution Suite 3.1

Server has 16gb Ram and 2 Tb Hard drive for the shared folder. Currently we have around 300 PCs being managed with another 300 soon to be added 

3 times in the past 2 weeks when ive remoted in to the server an error message is displayed on the screen saying 'Out of Memory'

It hasnt been running any tasks or jobs to cause the system to run out of resources. 

I checked the processes in task manager and there is only 5% cpu being used and 33% Ram being used. The only way to get rid of the message is to reboot the server. 

Has anybody else had this issue? 

Thanks