Car won't start

I have a 2006 vw Passat Every time I cut my car off
it won't start back up with out a jump ...the car
cranks like it's going to start but won't with out a
jump I've had my alternator , battery and starter
checked... my dash lights do stay on for a little bit
like 2-3 mins after I take the keys out of the ignition
.. so I started to disconnect the battery cable cords
when I cut the car off then connect them back
whenever I have to drive and that was working for a
week or so but now even when I disconnect and
reconnect the battery cords it still won't start with
out a jump . I took the car to 3 different places and
nobody can figure out what's wrong with the car