Immobilizer/ignition issue 1 series (e81)

[Justin_BMWe81]

Hello everyone!

My first post for me on this forum, i hope this is the right place to post. First of all a quick introduction.
I am the proud owner of a BMW 1 series (E81) for about 13 to 14 months, its an facelifted 118i from 2008. it's my first car en i enjoyed the journey so far, i do a lot of the general maintenance myself with the help of youtube.

However, after having driven about 35000 km without any problems, I now have some problems with (presumably) the immobilizer or ignition.
I have had about 3 times that I unlocked the car with the fob, then put the fob in the ignition and then nothing happens.
The car won't start, the dashboard doesn't light up (Looks like the whole car has no power) and I can't get the fob out of the ignition. After about 20 to 30 minutes the dashboard suddenly lights up and everything works again and I can then drive without any problems.

i also had once i was driving on the road about 80km/u, the car shut off for a split second all goes out on then turn it on.

I have tried to read as many post on the internet around this topic and i have tried a few.
The steps I have taken are as follows:
Check the batteryconnetions/wireinng are solid.
Use the spare key, both keys same problem.
Read obd2, unfortunately the only eroor code is my thermostat deafault in open position.
Replacing the battery, because the dasboard informed me in the winter that it was bad. Checked the alternator, gives around 14.4v while driving.
Replaced the battery of the fob.

This i read on some fourm but not sure it would help me.
I have read that the Immobilizer computerunit, the fob reader/ignition or the genaral wireing can go bad. i think deactivating the Immobilizer would be the easit soluion?

I saw some post telling that there were some known issues :with the fusebox, unfortunately i don't exactly know were to look for?

I also read that a bad fuel pump can cause simmelair issues, but it seems for me unlikely because i have no idle issues or stalling problems.

I hope someone could give me some advice about what steps to make next. or someone knows exactly what problem my car have. feel free to ask questions if something is unclear.

Best regards,

Justin.