Oh I almost forgot, it's also good to check what power profile you are using when plugged in to power, and unplugged. My guess is that shipped with a Dell preferred power saving plan applied, which is probably best. If the power plan gets corrupted, or is set incorrectly I have seen it cause issues. There are methods to restore the default Windows 10 power plans which work on most devices, but some really need the manufacturers profile to be applied.
Which Dell system is this exactly?