JuMP2start introduces a time-aware multicore stop-start approach designed for software-defined vehicle systems. By leveraging suspend-to-RAM, the system allows critical automotive services to resume in milliseconds rather than undergoing a conventional cold start. It coordinates suspension and resumption across a dual-domain vehicle management system combining a real-time operating system (RTOS) and Linux, while distinguishing between continuable and restartable tasks to prevent stale data from affecting safety- and timing-critical functions. Experiments demonstrate that critical CAN traffic processing can resume within 500 milliseconds of waking the RTOS, with steady-state throughput reached in under 7 milliseconds.