An advantage of trust in H'shem in respect to religious life is that he who trusts in H'shem, if he has means, will hasten to meet his monetary obligation to H'shem and to man with a willing soul and generous spirit. pg 359
It is clearly forbidden to expressly ask a non-Jewish mechanic to repair a car on Shabbos moreover even if there was no express request to repair the car on Shabbos but the mechanic would have no time other than Shabbos to repair the car that is considered as if he is being asked to repair the car on Shabbos and it is strictly forbidden to do so It is therefore prohibited to bring a car in for repair late on Friday and ask to pick it up on Motzei Shabbat immediately after Shabbos.