I had this issue for a while on one machine then it righted itself so idk the issue. That machine was running 2 accounts in full screen while my others are windowed, but that didn't change. I kept closing and reopening the launcher when that happened bc it was acting like the account I wanted to load was already in, though only the other was. That's why it closes on it's own after a bit.
It's possible I let a Windows update through that fixed it as I don't have them blocked on those machines, could try that, or switching to windowed if you're full screen. Why? Idk, but only factors that varied from my others.