I got it refurbished almost brand new, and I've had it for about a year.
Did you buy the refurb directly from Apple? The is the only way to get an Apple Certified Refurb.
Yes, RAM is the prime suspect but there may be something else—hardware; software; something fixable?—at play that is contributing. We can "see more" in this text-based setting if you post a system report. Fortunitely, there is a safe, secure way to do that.
If you want a data-driven evaluation in this setting where we can neither see nor touch your computer, please post an EtreCheck report. We can quickly and within the limitations of these forums help you determine what issues are at play without our playing a protracted game of "20 Questions" with you that could go on for days.
EtreCheck Pro is available here:
https://etrecheck.com/en/welcome.html
The free version will do nicely for this purpose, although the app is worthy of our financial support.
We can see hard data about drive performance, software issues and interferences, and RAM usage. Etrecheck is the development of a long-serving and trusted ASC contributor. It is a reporting app, not a "fix-it” app, expressly for displaying information in these forums to help us help you remotely. It will not reveal any personal or secure information.
Please see this excellent user tip on how to post long text reports like EtreCheck's into a forum response:
How to use the Add Text Feature When Post… - Apple Community
Please post the entire report. What seems insignificant to a new Etrecheck user can speak volumes to those of us who have reviewed thousands of those reports.