The radiator fan of my 2008 toyota sienna keeps coming on randomly, even when the car is OFF. Please help and be blessed

This happened to mine too, 2007, and I can't say it's normal even though people said it is, because the vehicle later over heated along the line and the engine packed up. So, always watch out for over heating, especially if you notice that the engine switches off on motion. Always watch your dash board.

folarr:
The radiator fan of my 2008 toyota sienna keeps coming on randomly, even when the car is OFF. Please help and be blessed

if a technician had worked on the car recently and touched anything related to your cooling system, then it's possible he had bypass the default connection.

if no technician had done any work, then you are looking at a faulty fan control module.

here is a similar case to yours but unfortunately majority didn't fix the issue while those who did don't even know what was done.

https://www.nairaland.com/4164165/car-fan-comes-randomly

Hello poster,
The information you provided is scanty. Rendering quality help is difficult.

For how many minutes or hours after engine turn off does fan operate intermittently? Is this non-stop?

Don't it happen even when engine is cold?