I had something of a similar situation with my 73 450sl a couple of weeks ago on a hot day. It stalled at idle, and almost did another couple of times. It started right up though. I haven't had the problem again. Someone suggested the car was particularly sensitive to oxygenated gasoline which is sold here in Calif. through February. Were you running on oxygenated gasoline? I know there are additives that are supposed to help this.