A space heater or electric fireplace if you have one are both great options. I use the Heta STorm Infrared Space Heater and it works great. Here are a few options that Rv’ers from this forum have recommended: https://camperfaqs.com/best-electric-heater-for-rv
My wife 😉 Jokes aside, an oil-filled radiant heater. They are nearly silent and dry the air like an electric space heater. The do take a little longer to warm up