Car seems to stall when shifting?

What is your question?

The car started having troubles a few weeks back, it would stall when i shifting in between gears or shifted into 1st. I changed spark plugs and fuel filter and the problem seemed to have cleared up but now it has started again. It only seems to happen within the first half hour or so of the car being on where it will stall intermittently. Once it has been on a while it seems to be okay. If you have any idea let me know! cheers logan