2005 320d E90 wont start up

[Ropperoope]

My car is a diesel 320d e90 2005 with manual transmission with the 120kw engine.
I have been having this new issue for a couple weeks that sometimes the car wont start up, plenty of energy in battery in a 5 months old battery. I can hear the starter rolling over easy but it just doesn't start up.
Changing the key doesn't help. Sometimes the car starts if I leave electricity on and key in place. I've been in 2 cheap'ish car repairers who cant get any fault codes out of my car. So my options are pretty much to take it to the BMW dealership which is hella expensive.
I'm just asking if there are any known problems in my car model that I should be aware of, to tell them start looking from there since they take a whopping 100+euro per hour I wouldn't want to have them searching in the wrong places

Sry for being a complete noob but I can hardly change my own light bulbs so lets begin with that..

[Paddywhack]

Did you ever get this sorted