Used Memory is 122M, which is needed for your OS and other essential softwares.
The most important thing to note is the load average. When the load average goes beyond 2.x or 3.x, that’s when you need to upgrade or increase your RAM and CPU.
Apart from the explanation given above, There could be 100 reasons why more RAM usage. Please read some of the following.
- System might be running some software updates
- System might be doing some routine task (crontab, scheduled task)