A "burnt plastic smell from car" can have various causes. The burning plastic smell typically means a component is heating up too much. The odor might also come with a burning rubber smell, depending on the cause.
Stop driving immediately: A burnt plastic smell is a sign that something is wrong, and it's important to stop driving to avoid further damage.
Look for any visible signs of damage: Check for melted plastic, frayed wires, or smoke coming from the engine bay.
Check your dashboard for any warning lights: Some cars will have warning lights that indicate electrical problems or overheating.
It's best to take your car to a professional as soon as possible. Call an auto repair shop in your area and describe your observations on the phone. Various burning smells can develop into serious issues. Make sure you can drive it to the shop so they will be able to diagnose the problem and recommend the best course of action.