If i hit a hard bump the engine will cut off,and just maybe after 5min. it will start up and run fine.What do u think

 

Some questions for you:
What year/model/type of engine?
When you hit the bump, does it immediately die or still run for a few seconds...?
What mods do you have?

Although it is tough to help you w/o those answered, a few things come to mind:

If you have a distributor, that is the first thing that occured to me. If u have one, i would check on the spark plug wires and the rotor.

Intermittent ground is very possible. I have seen a bad ground manifest as a buttload of different symtoms and have learned to never to take a ground for granted. Go ahead and unscrew the grounds you can find and clean/sand the ground area and terminals and reconnect.

If you have a multimeter and a Haynes/Chilton's, check the solenoid.

Last, I would check the alternator (belt at proper tension, securely bolted/immovable, maybe bench tested at Advance Auto Parts <free>).

Hope this helps for now...