So, this one is just strange, and I'm telling this one more as an anecdote than hoping for an actual solution.

I have a slightly older android phone that I'm currently using as a replacement for my usual phone which is in repairs. And I have a pair of bluetooth headphones.

And every time I connect those headphones to my phone... the phone automatically calls the last number I dialled. For about three seconds, then it hangs up. And I don't have the slightest idea why.

Luckily, I'll get my proper phone back in a day or two, so for now, I'm just not using those headphones. Got two or three very confused phone calls yesterday and today, though.