The Harley-Davidson Sportster 1200 can be suitable for beginners depending on their level of comfort, experience, and physical stature. The Sportster 1200 is generally considered a more powerful motorcycle compared to smaller displacement bikes often recommended for beginners. However, if you are confident in your ability to handle a larger and more powerful bike, it can certainly be an option.
As for your height, being 5'4" may present some challenges when it comes to reaching the ground comfortably on a Sportster 1200. The seat height of the Sportster models can vary depending on the specific year and edition, so it's best to consult the official Harley-Davidson website or visit a dealership to determine the seat height of the specific model you are considering. Additionally, you may find that adjusting the suspension or using a lower seat option can help improve your reach to the ground.
It's important to keep in mind that each individual has different comfort levels and preferences when it comes to motorcycle size and handling. If possible, I would recommend visiting a Harley-Davidson dealership or a motorcycle rental facility to sit on a Sportster 1200 and assess how well you can reach the ground and handle the bike before making a decision. Additionally, taking a motorcycle safety course is highly recommended for beginners to develop proper riding skills and confidence.