Hmm, I'm not an expert, but it sounds as though your lo may be overtired or overstimulated. This could be the reason for the jolts that you see. My baby, would often do this, and I adjusted his awake time, by very carefully watching for the first signs of tiredness. I would recommend swaddling, which helped Jacob a great deal. Initially I thought he didn't like it, but his behaviour was more to do with him being overtired. To begin with I would stay in his room waiting for the jolt to happen and then pat/sshh in the cot. As time went on, I found that generally he would jolt at the same times - 12 and 20 mins. So I could then intercept it by just placing my hand on his chest and applying gentle pressure. It did take a while but we got there in the end.
let me know how you get on.
Cheryl