Rattling at high speed in the engine compartment of Renault Laguna 2?

Hello everyone,

I am currently driving a Renault Laguna 2 and as the question suggests I have a noise problem.

While driving, at about 2.5 k rpm, there is a very loud but constant rattling in the engine compartment.

From the sound I would say it comes from the middle tending towards the right (in the direction of travel).

However, it is not an acute problem but every now and then, sometimes nothing for days, sometimes for days in a row.

What I could determine is that it could have something to do with rain and wetness; it never occurred on sunny and warm days.

I am grateful for any help.

(Workshop is currently not an option for financial reasons)

Edit: Additional information

Mileage approx. 146k km

Timing belt: "As good as new"