Limp mode at randon times

[Dawie #3]

Recently did my timing chain on a e90 2009 320i n46. The car performs and runs well on the open road until I get to stop or slow down at traffic lights or stop sign...at random times it goes into a limp mode making me crawl across the intersection. The rev drops as if it's going to switch off and drops low. If I switch off and restart the car runs normal again for a few minutes or hours.Ran diagnostic and nothing picked up. Anyone has a clue what this might be?