It depends on whether you want to start behaving like a sorcadin early or if you'd rather play something more stable before then. In a similar situation, I chose the former and went paladin for two levels before switching to sorcerer, then staying on that for six levels before switching back to paladin for four more levels. So Pal 2>Sorc 6>Pal 4> Sorc X. This lets you play like a paladin for the first two levels, and gets you a kind of sorcadin lite at level 3, with some of its more iconic abilities (quickened and twinned SCAG cantrips with smites) by level 4.
This route leads to some serious squishiness in the critical early stages of the game, though. Shield helps, but you don't really have enough spell slots to work it and your smites all that often. Make sure you take the defense fighting style if you go this route, you need every bit of defense you can get.
If you'd prefer to play it safe, stay a full paladin until you get to the desired split level before taking sorcerer. At least until level 6, for safety. Naturally, if you only wanted the addition of smites and heavy armor with shields, two levels in paladin and then everything in sorcerer will suffice for your build.