Every time I run VIM, "help.txt" opens automatically

if you run $ vim -u NONE

and the issue persists, maybe (like in my case) is some software simulating a key press to prevent the system from sleep.

try to change it for another key, like shift, and not f15.

good luck!

in my case it was because I am using app called caffeine (prevents PC from sleeping) which is simulating pressing F15. After I change it status to inactive, it stopped opening vim help in terminal window.

Try running:

vim -u NONE

If this help file doesn't appear when doing that, then there's something in a vimrc file somewhere that is opening the help. Check in:

~/.vimrc
/usr/share/vim/vimrc
/etc/vimrc

...and anywhere else you might find a vimrc file on your system.