Q: Car stopped running during use on the highway and won't restart.

Thanks for inquiring with YourMechanic. I believe your issue is going to be your alternator. The reason I am going this way is because your car isn’t starting and it just stopped running on your on the highway. The reason it would be your alternator stopping your car from running is because it drained your battery. Your battery can recharge with time if it is still a good battery. If you want to check it to ensure it is your alternator you can get a multimeter. Check it by starting your car and while it is running, connect the positive and negative probes to their respective places to and ensure it reads 14 volts. If it is anything less, it’s not charging your battery properly. Also, if you have to jump your vehicle to start it, once you take the jumper cables off and it shuts off on you right away, that is your problem. I hope this helps and I hope I’ve led you on the right track to fixing your car. If you need help replacing your alternator, I would recommend a professional mechanic, like one from YourMechanic do the replacement for you.