When the crash or freeze occur, try to look into the logs, maybe there is some clues about any issue.

Disk is a whole world, so I was talking to check not only the space, S.M.A.R.T, which stands for Self-Monitoring, Analysis, and Reporting Technology, is a system used to monitor the health of hard drives.

But... if you have a couple of dollars and don't have time, maybe it's time to migrate to a better hardware, some NUC with better performance for the next 2 or 3 years.

Downsize to the minimum that you need to cover your usual user case and focus on analyze that, less process is better to search root causes.