Hello,
This is a bug that I have endured for a while and happens all the time to me for some reason on both official and community servers.
Upon logging into your character, there is a chance that your weapon will fire itself automatically after you ADS for the first time.
I usually solve this by dropping the gun from my hands and picking it back up, this way I have never seen it fire auto.
However, its caught me off guard a few times and its now annoying me enough to report it haha, it gives away your position and it wastes ammo lmao. Not to mention it scares the shit out of me as I'm thinking there's someone right behind me.
Ammo for the good guns doesn't come very easy either!! specially on official.
I am probably not the only one reporting this but I assure you this is very real.