Fiesta Not Picking In First Gear After Traffic Jam Driving

[varwal]

I am facing a strange problem with my Ford Fiesta Sxi, 2006 Model, 70000 Km Done.

As such car is not giving any issue. In normal driving conditions it drives and works

perfectly fine.

Problem : Once drvien in heavy traffic for 1/2 hour or so in first-second gear after a while

car stops picking in first gear, it shudders, as if no fuel is reaching, a lot of gas is required. but if we put

second gear it perfectly fine.

this problem remains for long once occured. But if car remains off for some hours it still becomes normal.

-> As such car has new battery, recently serviced.

-> After new battery frequency has reduced, nd occurs after long traffic jams.

-> No smell, no temprature gauge increase, no excessive smoke observed.

Please HELP.

Varwal