I had same problem a while back. I too am new to my shield, although my first gun was a full size m&p 9mm.
At first, I was told the same, a limp wrist. Since then, the problem has gone away.
I also own another pistol .380 ACP, I thought the issue was also a limp wrist, however, there has been lots of complaints about same issues so I am sending it back for an upgrade and exchange of magazines, which seems to be the problem.