Based on your description it seems the issue is being caused by a power management on your system. My best recommendation is for you to update the BIOS to latest and install the graphics driver provided by the Computer Manufacture. This OEM driver contains special changes for your computer so I strongly recommend you installing Dells driver.
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Try going into the Control Panel, select "On Battery".
Then try disabling Display Power Savings or reduce its aggressiveness (move slider toward max quality), select Apply.
You could also try disabling Display Refresh Rate Switching.if it is enabled.
See if either of these help.