my mothers van has been very stubborn. she will start it and than the next time it will not start. new battery has been put in also. when starting it it starts real slow and than the engine runs smoothly. any reason for this vehicle to sometimes start and not start. we have had it to a shop and no one knows what is wrong with it
The connections at both ends of both battery cables must be clean and tight. Same for any ground wires or straps, especially between the engine and body.
The starter may be on its last legs.