Why does shotcut do this sometimes?

Shotcut sometimes overloads my CPU for no reason. I have a gaming pc as well! What is happening?

Hard to say with the amount of info given ;). When loading a project with many clips that will happen. If you add a lot of stuff onto and around the clips and videos quite likely as well. Video editing, in general, is a memory hog, so on bigger projects it could be that heavy use of a swap file (depending on your OS and settings), respectively the harddisk it is on, keeps the computer busy.

I’m no real expert there, just a few ideas what to look into.

I just loaded one clip which was like 5 minutes long to edit and then it started to use my cpu.

When a new file is opened in Shotcut, it needs to scan the file to get information about it. This can momentarily spike the CPU. Additionally, Shotcut will create a background tasks to generate the audio waveform picture for the timeline. That background process is set to be lower priority, but it can still spike the CPU for a while. There are certain operations that can trigger the regeneration of the waveform - like changing the audio track or changing the speed.

Maybe some of those features explain the CPU usage. In any event, if you are not actually playing video in the Shotcut Player, i would expect any tasks that are using the CPU to be low priority (so they should give higher priority to other applications on the computer).

Thanks a lot.