Jotinya

I have a Mercedes V-Class 220d van, manufactured in 2017. I have recorded the start from inside the van with my mobile phone, then I got out, we opened the hood (that's why you hear the motor noise more). In the 5 seconds after starting I hear a noise similar to a turn signal or a metronome or tic-tic-tic that disappears. I don't know if there is anyone with such a keen (and technical) ear to give me some advice. It can be heard at this link to my Drive and I also attached the mp3 file. Thanks for the help!

https://drive.google.com/file/d/1KRDp77fJjAJI68PYxwy2ivCD40kVho8d/view?usp=drivesdk