When I go to start my car all is fine until I go to turn it over.. That's when the car losses all power to everything. I can only get the power back by slamming the driver door or by hitting the under side of the dash next to the hood latch..? It does this randomly and usually 5+ times before I can actually start the car.. But once started everything is fine.. I also have had this black out while driving.. Everything turns off except the engine and than turns back on in a split second..

The dealer tried telling me it was a battery.. That they could replace for 200$..

 

Have the battery tested by an auto parts store, test free New battery much cheaper.

But, my guess is the under hood fuse box has become separated.

 

Obviously it sounds like a loose connection.

Have the battery tested as donbrew suggested.
I would also check the main positive wire connection at the underhood fuse box.
There have been a few posts on this forum about this being a trouble spot.

 

mine does something similar when i go to start mine it shuts down the car. i have never tried hitting the dash or slamming the door to manly for me to attempt those feets. i just go under the hood replace the fuse off on my merry way again. And i have to continue to do this because i cant get the part i need to fix the underlying issue

 

My car did this same thing it was a loose connection to the under hood fuse box as stated above. Here is the cable that was loose on mine.