Hey Jan-Vidar, you'll need to get more information to determine what the best steps to take are. I would recommend using a tool to collect performance data on your host(s) over time that includes tracking on process-level resource consumption. There's TabMon, or you could use the Resource Monitoring Tool included with the Server Management add-on, or you could do old-school PerfMon counters. Once you know what process is using up your resources you'll have a much better idea of what to do. I would not recommend deploying patches unless you are very confident they will solve your issue--and for that, you need data.
If you are using 2018.2.0, we had similar issues going on. Then we did lot of Load Runner & TabJolt testing and we worked with Tableau also then we came to know that that specific version had lot of issues which were fixed in the latest versions like 2019.3.x .
Hope that helps and good luck
Tableau Support can assist with any issues with your server. I suggest entering a support ticket so they can take a look. If you are an enterprise customer, I'd also involve your Tableau Sales Team as they have tools to help diagnose issues.