Follow through
You are anticipating the recoil and flinching. Your shots are going low (and maybe left or right). This is a problem many shooters have with the DA pistol--the anticipation of the 1st DA shot knowing that subsequent shots are SA. If you want to master the SIG pistol, learn to do a double tap-DA then SA. Quickly. Close range only, at first. Shoot no faster nor farther than you can hit the target with each shot. Then increase the speed and range as you progress. If you're not willing to master it with losts of practice, I suggest you buy something simpler to learn. Like a Glock. Personally, I prefer SIG pistols and carry a P228, or P229.
Do this: Shoot a couple mags DA only, decocking after each shot. You will shoot good groups when you get the hang of it. The secret is FOLLOW THROUGH. It is achieved by having TWO sight pictures for each shot. The original sight picture, and the second one after the gun recovers from recoil. You can't flinch prior to the shot that way.
Incidentally, the two sight picture rule should be used for single action shots, also. They are not immune to misses from lack of follow through, either. You will notice after a bit, that the gun recovers from recoil as fast as it recoils--instantly--and comes right back on target IF your grip is correct. You can still shoot fast at multiple targets. Professionals are taught this method without re: to type of gun. FOLLOW THROUGH!
NOTE: the emphasis on focusing on the front sight achieves the same thing, since if you're on the front sight, and it's on the target--then you have accomplished FOLLOW THROUGH and though shalt hit the target. The front sight is your salvation, so don't lose it on the 1st DA shot--or subsequent shots, either. At extremely close range, accurate shooting can be done by using the front sight as a reference only---but that's a whole other discussion.