Picasso 1.8 16v Motor Fall is suddenly

Hello to all the foreros, I need help I am desperate. I have a Picasso 1.8 16v gasoline and for a week when I go, suddenly, I once let it stand for a while and starts but when walking 5 minutes it stops again and it does not start the stop and the next day and the next day it starts again, but shortly after again this does this in progress running out the motor failure and stops circulating. I take it to a workshop they put the machine and come out several errors and tell me that it can be the spark plug coils € 140 and when walking 10 minutes the same thing happens, and I do not know what to do, I have looked at the forums and I find nothing because most are gas-oil, they have told me that it can be the positioner of the cams Ono will find it. Someone can guide me I can not change things without knowing and the thing is not for purchases, I plan to buy the camshaft position detector because they have told me that if this failure stops the engine but I am not sure what to do good I hope someone can help me greeting everyone and thanks.

My Picasso's engine is the 1.8 gasoline model 16V G-6FZ EW7J4