We’re going to need some more information on what’s going on. The best way to track down performance issues is to study and practice the following docs: Performance and Profiling | Unreal Engine Documentation
If you’re new to this however, I recommend you start here: Performance and Profiling Overview | Unreal Engine Documentation
Are you working in a source build, or did you download UE from the launcher? Since you’re only experiencing performance problems when in the Shipping configuration, you’re going to have to package the “Test”-configuration. Test is a configuration that’s like Shipping, but with some profiling tools enabled. However, the test configuration is only available when you build from source. You can read more about Build Configurations here: Build Configurations Reference | Unreal Engine Documentation