Which Shield device do you have?
You could get great improvements replacing the internal mechanical hard drive for a SSD.
Did it for mine, and the speed improvement is very noticeable. Specially when updating or rebooting the device.
I used this guide, and I'm still seeding the drive image torrent: https://xdaforums.com/t/nvidia-shield-tv-ssd-done.3402580/
There, fixed it for ya.