This happens frequently, and I'm not sure if it's tied to the spawn menu keybinds to switch classes before joining the fight, but I will be playing one class consistently and unknowningly will spawn in and be in a different class.
Happens to me too, confirmed I am not making any inputs whilst on the death screen that this could even be attributed to, (which it couldn't do anything anyway because you can't change classes with Q & E without the spawn screen being fully loaded) extremely frustrating and MUST be fixed ASAP.
After you deploy, this screen fades out in ~1 second, but during the fade out it's still reading your inputs even though it's also executing whatever action you've bound to Q or E.
Largest thread on this, reply and upvote for visibility: https://forums.ea.com/idea/battlefield-6-bug-reports-en/deploy-screen-class-keybinds/12737636?topicRepliesSort=postTimeAsc
