htaccess file keeps changing by itself?

good day

My .htaccess file keeps changing, and when it changes, the website reports an internal server error and the website goes offline?

The htaccess file is supposed to be like this:

<Limit GET POST>
order deny,allow

# BEGIN WordPress

# END WordPress
</LIMIT>

however it keeps changing itself to:

# BEGIN WordPress

# END WordPress

how can I prevent it from changing by itself? as each time it happens my website goes offline?

any help would be greatly appreciated
thank you