I have the same symptom (car is e39 530):

Hazard lights come on, doors unlock & the dome light comes on. I have no water seepage.
Sometimes it does that while driving - I noticed it does that when the auto lights turn on.
I am inclined to think it's a weak battery. I will have to test it thoroughly. I was/am worried it's a failing LCM or GM3 module. Hope it's only the battery.