loose gearbox?

Hi all

Didnt really know what to put as the title lol basiclly I've noticed my car seems to be very very jerky in slow moving traffic.

Eg. Your in 1st/2nd gear low revs, no matter how gentle i lift my foot off the gas it seems to "jerk". Its very annoying and not sure what it could be. Ive had my car about 5 months now and i've only really started noticing it past couple of weeks. What could be causing this? Loose gearbox mount? I took it back to where I got it from a while ago and they said the mounts seem fine, (i thought i had excessive play in the stabilsier bar)

Any ideas?