Trying to ID a novel in which the protagonist (one of a number of Bourne-like trained agents) was repeatedly sent back in time to pull forward various individuals for training by the people of his time. A risk to such agents was that eventually they would slow down and freeze up. I vaguely think the character's name was Jerry, but that could easily be wrong.
They thought the freezing was due to the repeated temporal transportation, but turns out it was because their supervisors continually blocked memories of missions, and as the blockages added up the freezing began to happen. Somehow the protagonist's blocks are erased, and he remembers all his past missions - including one in which he was married and his wife was killed. Conflict with his supervisors ensues, at the onset of which one of them says a code phrase to him which is supposed to trigger a self-destruct implant in his brain but which he had previously found out about and deactivated.