Less than 6 month old Fire HD 10 tablet has vertical and horizontal lines on screens. Horrible and restarting doesn't help.
Try rebooting: Make sure it's charged, unplug it, press and hold the power button in for 40 seconds (ignore prompts), then release. Press the power button to restart if it doesn't begin to boot up on its own after a moment or two.
If rebooting doesn't help, contact customer support - https://amazon.com/contact-us
Sounds like a damaged screen. As mentioned above, talk to customer service to see if you're eligible for a replacement.
You can always reach customer service for help here: amazon.com/contact-us