newby-vr6 stalls and wont start sometimes need help!

Hey there I'm new to this forum. Ive had my jetta for almost 2 yrs now and it does this thing to where sometimes it just doesnt want to start or it could be ideling and just shut off. When it doesnt start it starts and idles up then just shuts off. I dont think its the fuel pump. I hear it giving pressure then stops when it builds pressure. I changed the fuel filter. The dealership said they dont know unless something breaks but there is no code poping up. I did do some researching on here and found maybe it could be an ignition problem? Any suggestions would be helpful please! Thanks