The Watchdog Timer is a security feature. If you don't "pet" it (refresh it) or turn it off within ~40ms of startup, it resets the chip. Solution: Always call WDT_A_holdTimer() as the first line of main() .
Because this is an embedded introduction, you must learn the difference between tail-chaining (quickly firing consecutive interrupts) and latency . The MSP432 can enter a low-power mode (LPM3) and wake up via an interrupt in less than 5 microseconds. The Watchdog Timer is a security feature