Sounds like he might be a bit stressed for some reason. Loud music, room traffic or any other noise/vibrations. Try giving him a snug hiding space (where he is touching on all sides) to make him feel secure. Leave him alone in a quiet space for a week or so.
This seems to work well for me. (Although one of my hets is ALWAYS ready to snap...constant PMS is my guess )

Best of luck and let us know how he does.