Mysterious Loose Part

I have a Peugeot 206 1.1L (02 plate) Petrol which I intend to take to a garage soon to address the following: When I drive over a bump, even small ones, I hear a rattle/knock that sounds like it comes from the drivers side under the bonnet in front of the steering column, this is becoming more frequent which suggests to me that the part is becoming more loose. None of the immediately reachable parts under the bonnet seem to be loose. I would like some speculation as to what the loose part may be based on the car make / model please. Thanks.