Get-Counter '\Process(*)\% Processor Time' | Select-Object -ExpandProperty countersamples| Select-Object -Property instancename, cookedvalue| ? {$_.instanceName -notmatch "^(idle|_total|system)$"} | Sort-Object -Property cookedvalue -Descending| Select-Object -First 25| ft InstanceName,@{L='CPU';E={($_.Cookedvalue/100/$env:NUMBER_OF_PROCESSORS).toString('P')}} -AutoSized

I got it from this reddit post from this sub reddit:
https://www.reddit.com/r/software/comments/e8co8m/lag\_until\_i\_open\_task\_manager/
Found the problem but this could be useful if you have a virus that detects if taskmanager is open or not. This one even detected when I opened Process Explorer. That command was the only way I couldve seen it.