The Haunted Sat Nav

No, I haven't gone bonkers. I KNOW that voices come out of a sat nav. This is a bit odd though.
I have the sat nav in a little basket in the kitchen with other oft used odds and ends. I hadn't used it in over a week. To switch the sat nav on you have to press and hold an inset button for a few seconds (it's inset so it can't be switched on accidentally).
I was having a conversation with a mechanic friend in the kitchen. My car had been giving me some trouble, and the mechanic said that this time he is confident that the problem had been fixed. He then said "let's just hope it's fixed this time". Then my sat nav suddenly issued forth with the command "turn around when possible". Not only did this seem vaguely on topic, but this shouldn't be possible. Firstly it can't switch itself on, and secondly it would have had to plan a journey to give directions. If someone has a simple explanation I would love to hear it.