I still don’t know what camera you’re shooting–you haven’t told me! It’s important to give all the information available when asking for help, otherwise every piece of information we give you is a complete guess. I’m going to assume that you’re shooting a DSLR, possibly a Canon Rebel? The following information is based on that guess. If it’s wrong…sorry. Tell me what camera you’re using, and I’ll be more specific, more helpful, and less grouchy 🙂
The reason the auto-exposure adjusts all those settings is because that’s what auto-exposure does! If you’re wondering why its changing the shutter, it’s because DSLRs’ auto-exposure programs are designed for still shots, so a fast shutter speed is desirable. It’s not in video.
You don’t want to change your shutter speed from 1/(2 * framerate) unless you want a certain look. If your shutter speed goes too high, the video will look choppy due to reduced motion blur, while if it’s too slow, the motion blur gets out of control.
Frankly, you’re NEVER going to get a good result using an auto-exposure mode on a DSLR. Never. If you let the camera control the shutter speed, you get weird motion blur artifacts as described above. If you let it control the aperture, you get weird flickering exposure changes because DSLR apertures snap to certain set apertures, rather than smoothly transitioning. If you let it control ISO, you get some the same exposure changes, coupled with changes in the amount of grain in the image as the ISO goes higher.
TLDR: Don’t use auto-exposure on a DSLR for video. It sucks. It’s better to find some manual settings that generally work for your scene, and just deal with a few small changes in the exposure. If you’re shooting a vlog that requires you to go from inside to outside, shoot two takes, one for inside, one for outside, and cross cut when you go out the door. It’s better than the horrible problems that cameras create because they’re not as smart, or as capable, as human operators.