Windows 10 volume randomly jumps to 100%

It's a driver (Realtek supposedly) problem with Windows 10 that causes this issue: when playing a video (YouTube, local file, etc.) and you pause the audio, playing again would result in a volume change without any real change in the speaker volume meter.

The following fixed it for me:

Source: Windows 10 Maxes Out Volume Sometimes

1. Click Start > Type sound > Enter to open Sound settings
   (Alternatively, right-click on the tray area Sound icon and select Sounds)
2. Playback tab > Right-click Speakers > Properties
3. Enhancements tab (if existing) > Uncheck Disable all sound effects (or similar option)
4. Uncheck Immediate Mode at top of the list

EDIT: For users that have Advanced tab instead of Enhancements:

3. Go to Advanced tab
4. On Signal Enhancements section Uncheck Enable audio enhancements

I have fixed the Windows 10 audio issue on my laptop by doing this:

1. In the lower-right hand of the screen, click system tray.
2. Right-click the audio icon then click Sounds.
3. A new window appears. Click the Communications tab.
4. Click the radio button for Do nothing and click OK.

My machine was interpreting something as incoming or outgoing communication, thus initially lowering the volume.

The audio driver you have looks to be very limited, with a very lacking Enhancement tab.

Try to find a new driver for it on the Realtek website.

If you want us to help, please go to Device Manager, and under the Sound branch enter Properties, and report the value of "Hardware Ids". Post also a screenshot of the entire Sounds branch.

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According to the Hardware Ids, your sound device is the Realtek High Definition Audio.

I have located two possible drivers in :

1. Microsoft Update Catalog (requires Internet Explorer)
2. Realtek High Definition Audio download

I suggest to try them both in the above order, doing each time :

1. Download and install the driver
2. Delete the Realtek device in Device Manager
3. Reboot and test

If both drivers fail, then the problem is with Windows 10 itself, and the only advice left is to downgrade back to your previous version. If you decide to go this way, see this other answer of mine.