Thanks all for your input.
These all sound like potential issues, I guess I just don't understand why it comes and goes the way it does. I better just get it into the workshop. The only problem I have is, I hope it actually rears its ugly head when it does go in so I can show my mechanic what I'm actually talking about! That's why I just wanted to go armed with some potential causes so, once again, thanks everyone for the feedback
Originally Posted by andrey_gta
In South Africa a user had an issue with a faulty throttle pedal. Mentioning incase other leads show no help
I didn't even consider that, but I suppose anything's possible. I'm based in ZA as well, I wonder how common this problem is here. Could be the way we drive, BMW drivers have got a bad reputation for being the most aggressive on our roads haha