Hey Ann2012X,
Welcome to the Apple Support Communities! It sounds like you're running into an issue with your wireless charging pad working in conjunction with your iPhone. I'd be glad to look into this with you in more detail.
Optimized Battery Charging uses machine learning to learn your habits and patterns when charging. This also includes specific locations, such as work or home, which may be why you don't have an issue in the car, as Optimized Battery Charging wouldn't be in use at that time. As I mentioned, it works on habits and patterns. Have you adjusted your charging patterns at all? This could be important because your iPhone can charge differently when using that setting. For example, it can be plugged into a charger or on a charging pad and not be charging for a while, based on your normal charging rituals. This is especially true when charging past 80%. More info on Optimized Battery Charging can be found below.
About Optimized Battery Charging on your iPhone
Thanks!