Intermittent jerking in 3rd

Just wondering if anyone else is having this problem. I've got an '04

2.5 RS. When I'm in 3rd gear (and only in that gear), I sometimes get a small jerking motion (kind of feels like the sparkplugs are misfiring) for one second the instant I lift my foot off the accelarator. It seems to happen randomly and cannot always be reproduced. It started 2 weeks ago, and I know for a fact it never did that before. The service manager was in my car to check it out and claims that's normal, although that's impossible because it didn't used to happen.