I get the feeling that Stafford seems to have these screw ups early in the game when he feels he can take chances and make up for them. There has to be a reason it happens primarily in the 1st half (1st q even) and then he settles down and doesn't do it anymore (mostly) for the rest of the game. It's like he has an "Oh @#$%&" moment and then realizes he can't be too loose with the ball from that point onward.
I am not sure if it's him or the coach putting him in spots early in the game that he shouldn't. You said yourself that our D is built to play with a lead and maybe that's why he feels pressure to make plays that are not there.
All I know is my confidence for Stafford playing 4 good games in a row is very low. I feel almost as low as I did with Goff when it comes to winning (albeit for slightly different reasons) and it sucks.