I'm not sure how many processes you are running, but you can check:
run this command line::::
grep processor /proc/cpuinfo | wc -l
Then run this command line to know how much free RAM you have:
Then you can run this command to know how much space used and un-used:
And if the RAM used is a lot, It is better to restart your VPS from the DO cntrol panel and then run free command again to see the difference.
if your disk is full, possibly your tmp folder is full.... you need to empty it