Lights Spontaneously Flashing and Draining Battery

[vicmedici]

I have a Ford Explorer Sport 1999 with 120,000 km. Last week I discovered that the parking lights turn on by themselves for short periods during the night. This happens when the vehicle is parked and the keys are not in. I suspect some sort of shortcut. The result is, some mornings I have to get a battery boost from someone else because the lights have drained the power.
I talked to a few mechanics and no one seems to know where the problem is. Any sort of help will be greatly appreciated. Thanks in advance.
Victor