You might think I'm crazy but I promise I'm not, this is completely weird.

The car has been doing this since a couple days and we can't figure out where to start.
It's cold where I am, - 20C average. Car starts fine, runs fine, no errors, tires are good, brakes are good, doesn't pull to a side if brakes are applied, no noise going over bumps or if the front wheels are turned either direction.

Start driving, no noise. After approx 30km highway every few seconds you can hear a sound like 2 plastic cups smacking against each other. Having the heater/fan on full or off doesn't change it. Speed needs to be at least 80 km/h.
Looked under the car but nothing is hanging down or seems out of place, looked under the hood but everything seems tight and in place.

Oh, forgot to say, the noise is coming from the front driver side.
I would assume if something is hanging loose under the car you would hear it no matter if the car is hot or cold.
Once you park the car and it has time to cool down it will take again about 30 - 40 km highway before the noise starts again. At first in intervals of about 3-4 seconds but the longer you drive the interval becomes shorter to maybe every 2 seconds, all the time just one tick, knock or what ever you want to call it, like two plastic cups smacking against each other.