Just got my 380SL back and repaired similar problem. It would run for about ten seconds and die. Problem was fuel distributor, it was beginning to go bad. Have mechanic check the diaphram in distributor mine was bad. If you need a new dist go online to get it. Dealer charges $3200, most places $1000-$1200. Online at German Star or ********Az $450. Dealer Mechanics suck when it comes to our 20+ year old SL's try to find a good independent Mercedes Mechanic.
Good Luck