How to restart void loop if condition is met
When programming with arduino IDE, you declare 2 functions, setup() and loop().

Before compilation, arduino IDE basically expands to :

int main(void)
{
    /* run the Arduino setup */
    setup();
    /* and the event loop */
    while (1) {
        loop();
    }
    /* never reached */
    return 0;
}


So, from here you can see that setup() is called once at startup and then, loop() is called in an infinite loop. 
Il you return from within your loop function, it will be called again.