SQL Server Express 2016 high CPU Usage as soon as I log into Windows I have a Windows Server 2012 R2 configured for ASP.net applications that connect to SQL Server 2016 Express installed on the server. This server is a VPS with 3 cores and 1.5 GB RAM. The load on the server is not high at all. 

I am having problems with the servers CPU Usage. Some seconds or minutes, as soon as I log in to the windows account through RDP, the SQL Server process starts consuming between 15% and 33% of CPU constantly, which is equivalent to using 1 CPU almost completely. 

I first checked for running queries with SP_WHOISACTIVE and there are no running queries. (http://whoisactive.com/) 

I then followed the instructions at: http://logicalread.solarwinds.com/troubleshoot-high-cpu-sql-server-pd01/#.V2xtwLvhCUk
and have found that the culprit is “% User Time” when diagnosed by the performance monitor. 

I have not been able to identify what the problem is after this point. All I know is that as soon as I log into the windows account, the CPU starts being consumed. As soon as I log off, the cpu usage of the process drop down to below 3%. Sometimes, while I am logged into windows, the cpu usage drops for some minutes, but it goes up again. I don't have to open any specific Windows application for this behavior to start. 

Does anyone know what could be happening?
as Aaron pointed above, the problem actually was related to having only 1.5 GB of RAM memory. The server was upgraded to 2 GB or RAM and the problem was solved.