My Mini Cooper 2003 suddenly started stalling when coming to a junction or traffic lights. I took it to the garage and a key fault was identified. So I bought a new key. However it is still intermittently losing power when not warmed up and has stalled a couple of times since then. Any ideas? I am reluctant to take to a mini garage but feel I might need to? It is quite stressful not knowing if it will stall. Thanks for any advice.