2000 1.8t wont start

Hello everyone, im new to this room. Well I hope you guys can help me with my 2000 jetta 1.8t starting problem. About a week ago i started my car, and the throttle needle jumped up and down. And wen i started driving I noticed that my car started hestitating when i accelerate after a stop. On the freeway it wud not go faster when i step hard on the accelerator, and the check engine light started blinkin. And today i tried to start, it would not start. So i jumped and it start. But I went to the dealer and they checked, they told me that the battery is fine. But i put in a new bat anyways. and after i started the car, it starts but then it shuts off after 2-3 sec. And when i drive to the mechanic to have it check, the car wouldn't start again after i turned it off. I've recently have my 40000mile service. spark plugs changed. one of the mechanic told me it could be the alternator. but i heard ppl said it can be the fuel filter also. oh by the way, when i started driving to the mechanic to check, it didn't go past 25mph. and sometimes it started jerking. please help me..im poor and the mechanic keep tellin me to change everything...

one of the mechanic just told me recently that it's because of the codes PO302 and PO301 which is misfired detected on two cylinders...i don't know if he's telling me the truth. And in the past i have another mechanic look at it and he told me my 02 sensor behind the cat is bad, that's why the chek engine light comes on. but now the code does not show it anymore...im wondering why?

1.8 ignition coil failures are common. The codes are for cylinders # 1 & #2.

thanks for the reply boschmann. but i have another problem. after the mechanic fixed the misfired code. the car became overheat. and this never happen before. and he told me to change the thermostat, so he charged me for it, and it's still overheat. so he told me to change the water pump...ahh so much prob. I don't know if i should trust this mechanic. Is it true that after you change your battery everything is erased? and the engine has to learn everything over? thast's wut he told me. does misfired cause the engine to shut off after you start your car like for a couple of sec?

Fixed or just reset the code? If the water pump isn't leaking then I doubt it's causing the overheating. Has he checked for head gasket problems (compression)?

He told me that he switched the coil for cylinder #1 to #2 and #2 to #1. to see what happens. and after he did that. he started the engine for a bit then the engine became overheat. i doubt that the water pump is leaking. but he insisted that the water pump doesnt work that cause the engine to overheat. could it be just a sensor or gasket? my other concern is why does my engine still turing off after it has started for a while? is it the ignition coil on cylinder one and two that cause it? because he didn't put a new one in, but just switch it around. ONce again..thanks boschman.

I can't remember if your car uses a power output stage ignition module like a Passat or not, they commonly lose #2 cylinder but I don't think your's uses one. I've only seen one car in 20+ years overheat due to a faulty water pump impeller (not leaking). The combination of overheating & missing is not a good sign, I'd make sure he checks it out for a head gasket problem.