Where is my gold going?

I have noticed four or five times, when loading into a new map or logging in/out, a massive amount of gold is just GONE. I am not buying items, I am not respeccing or anything that would require a huge amount of gold - this last time it was nearly 30 million gold, gone. I went AFK, the game kicked me, I logged back in and only half of my currency remains.

And as I said, this isn’t the first time. How am I supposed to save gold for the later stuff if half of my stash just up and walks away out of nowhere??