@Members_RacheleB: I'm sorry to hear that you're experiencing this issue with your Galaxy S20 FE. To get an understanding of what might be causing your battery to drain, next time the issue occurs please head to Settings > Battery and device care > Battery > Tap on the usage graph, then scroll down to check the breakdown of your usage. Are any apps or features listed that are using a high percentage of battery? If so, tap on the relevant app > Limit Usage, and add it to the Sleeping or Deep Sleeping apps folder to limit its background usage.
I'd also recommend disabling Wi-Fi and Mobile Data while the phone isn't in use overnight, and closing all applications by tapping the Recent button in your Navigation Bar (3 vertical lines) > Close all. You could also swipe from the top of the screen to the bottom using two fingers, and enable 'Power Saving' via the Quick Panel. Let me know if this helps.