frustrated11

hey guys, I have a 97 Chevrolet k1500 with gsr 400 in it. it runs great most of the time but it will sometimes just cut off and will sometimes crank but then shut off again.after awhile it will crank and run fine until it does again.took it to 2 shops and they cant find it. shows no error codes on computer.fuel pump comes on even when it is acting up. no lights come on dashboard at all.it is a totally random event that happens rather you are idle or driving down the road.