Dell support fixed my issue remotely, sound driver was causing the problem, they just installed the latest Realtek audio driver (Realtek SoundWire HW Audio Codec Device Driver) which was missing in the Device manager.  
I got this laptop 3 days ago (Jul 18, 2022). It is really nice in many ways, and when it's going full power it is fantastic. Unfortunately, it likes to dip below full power and throttle itself to a grinding halt way too often. It throttles to 0.4 ghz, which is slower than computers I owned 20 years ago. I have set it to Ultra Performance mode in Dell performance settings. I have set the power in windows settings to Best performance. Still, this thing will throttle down to 0.4ghz (based on task manager reporting) when I open spotify or youtube, or work on a big powerpoint presentation. Sometimes if nothing is open it will even throttle itself. The laptop isn't running hot or anything. CPU usage is less than 5% when this happens.  It just likes to throttle really hard all the time. A restart will prevent this for about 30 minutes, then it decides to throttle again. Did I get a lemon? Am I missing something?
Dell XPS13 Plus 9320 Throttling way too hard, way to often, down to 0.4ghz