Mazda 626 GW, jerking when accelerating

Hello, with my Mazda 626 GW, Bj.99, 85kW, 75tkm, I noticed for a few days a short jerking while speeding up. So far always in third gear at approx. 2000 rpm. For some time my fuel consumption has also slightly increased. I rarely come more under 9L, which was not a problem before. Does someone have a tip, what is announced? Greeting Peter