This may be the .net Framework compiler going at it when idle. What i do once windows is installed and fully updated is to manually run ngen.exe executequeueditems command and have it do all the compiling in one go. Then no more random cpu usage. I run that command after doing windows updates once every 2 months or so. I got auto updates disabled so manually run it once in 2 or 3 monthsI have noticed this with win 10/11 , but it could be improving things? Plus win 10/11 doesn't do this all the time.