Dropped Phone, what component went bad?
Phone keeps restarting by itself. Sometimes when i am using it other times without me touching it. What can the problem be?
That sounds bad, hopefully it can be a ribbon that has been moved a bit from its place, but seems like the board has been damaged.
The procedure is to open your iphone carefully and check all the ribbons attached to logic board. Check if they have moved, or even better, disconnect all and reconnect them again.
Inspect if some component has blown or logicboard part has crushed.
You can follow this guide to reach the logic board : iPhone 5逻辑板更换
Best of luck!