2018-08-29 Linux Headers

Way 1
From: https://ubuntuforums.org/showthread.php?t=2221389

Re: Deleting Old Linux Headers?
Thanks.

So the latest kernel and headers are from 3.8.0-39. That's is the one you are using right now and it shouldn't be removed.

Also, I'd keep the previous one as safety practice (3.8.0-38).

Then run this command:
Code:
sudo apt-get purge linux-image-3.8.0-29-generic linux-image-3.8.0-35-generic linux-image-3.8.0-36-generic linux-image-3.8.0-37-generic
Now the the kernels those kernel are out of the picture, you can remove their headers:
Code:
sudo apt-get purge linux-headers-3.8.0-29 linux-headers-3.8.0-35 linux-headers-3.8.0-36 linux-headers-3.8.0-37
Let us know how it goes.
Regards.

Way 2:
https://unix.stackexchange.com/questions/445669/how-to-safely-remove-old-kernels-headers-and-libraries

sudo apt-mark auto '^linux-headers-[34].*'
sudo apt autoremove