Something’s using a lot of CPU. That’s not particularly uncommon – games want to use a lot of resources.
You might want to open up a profiler and figure out what, specifically, is using the CPU. There are some profiling tools built into Unreal, and you can also use a stand-alone tool like VTune (if you’re on an Intel CPU) or AMD-uprof (if you’re on an AMD CPU.) If you’re not building the engine yourself, you will also want to download/install the source and debug symbols for the version you’re using in the options in the EPIC launcher.