I did locate the C-States control under BIOS > Performance and will be monitoring.  Hoping for a better solution, but for now I would just appreciate being able to type!
All, I recently received a new Latitude 5420 for my office PC.  I use it via WD19 dock via USB-C and since I started using it I have issues with repeating keyboard.  I get entries like "Final Draftsssssssss".  It seems to be random keys in any application.  Occasionally, I feel like the mouse freezes for a split second.  I went through three wireless keyboards and two wired keyboards.  Tried a WD15 dock.  All of my drivers and firmware are updated on the laptop and the WD19 dock.  Dell recently came and replaced the motherboard.  All with the same results. I have read similar with other Latitude laptops in this form, advises to disable the "C-States" in the BIOS and I understand that would reduce my battery life when I am mobile, which is not ideal, but better than a key getting stuck on delete and deleting email or whatever else I am working on.   I didn't see a clear "Disable C-States" in my BIOS, can anyone recommend what to look for?  Still an issue that dell is working on?
Latitude 5420 Repeating Keyboard Entry & Mouse Freezes w/Dell Dock WD 19 USBC