dnd 5e – Should a dragonborn Draconic Bloodline sorceror have only 4 starting skill proficiencies?

Yes, a Dragonborn sorcerer only has 4 skill proficiencies: 2 from sorcerer and 2 from their background.

That said, there are only 3 classes that grant more than 2 skill proficiencies: Bard and Ranger gain 3, and Rogues get to choose 4. Having only 4 proficiencies is therefore quite common, unless your Race grants additional proficiencies, e.g. Elves (Perception), Half-Elves (Any 2) or Half-Orcs (Intimidation).