You can use Unity's Editor Profiler to analyse performance (Window > Analysis > Profiler > Editor). In the Profiler, switch to the editor category and look for spikes in the graph at “Reload Scene,” “Reload Assemblies,” or “Awake/OnEnable.” After identifying the spikes, you can disable different GameObjects or functions to determine which one is causing the delay. Additionally, keep in mind that deep and large meshes can also contribute to performance issues.

(If hadn't done yet)Also, if you don't want to reload the domain each time you enter play mode, you can just go to Settings and Disable "Reload domain on entering play mode". It helps to instantly enter play mode.

You can use Unity's Editor Profiler to analyse performance (Window > Analysis > Profiler > Editor). In the Profiler, switch to the editor category and look for spikes in the graph at “Reload Scene,” “Reload Assemblies,” or “Awake/OnEnable.” After identifying the spikes, you can disable different GameObjects or functions to determine which one is causing the delay. Additionally, keep in mind that deep and large meshes can also contribute to performance issues.