There is more than 1 way to do this. With a bump and go it is a bit complicated. Best way is to remove the rectifier in the trolley and run the track on DC. This can be made with a bridge rectifier. With a couple of relays and some insulated rails on each end you can reverse the trolley electronically by reversing DC polarity. Adding a modular timer will cause delay. Mid stops can also be made with insulated rails along the route. I have done this but do not have a diagram handy. I think you would need 2 relays,a bridge rectifier and an outside insulated rail on each end and a modular timer. For stops along the route,you would need maybe a third relay. The relay coil on one end will latch electrically (via the outside insulted rail method) and the relay on the other end will unlatch it. Remaining contacts will reverse track polarity and start an interval timer module.
If using the bumpers,it is hard to get it to run reliable. Too fast and it derails,too slow to the bumper and it stalls.
Dale H