Repls typically go to sleep after a period of inactivity. To make sure that your Repl is restarted, you can use the Always On Power Up.
If you want to make your Repls more powerful, you can use the Boost Power Up to increase the number of vCPUs and how much RAM your Repl has.
With a free Replit account, personal Repls are public by default.
If Boosts aren't enough, you can add GPUs to your Repls to make them even more powerful.