I had a 335i that would do that. It was nothing to do with the speed
setting. If you pulled out on the road and had to give it gas to
merge into traffic. Would chime and kill power and say limit.
had the speed set high so was not that. Took it in a couple of
time but never found a code or something wrong. Got so if
had to merge made sure had room, because if it killed the power
another car could run up on you fast.