My laptop screen appears to be rotated in tablet mode, even when I am in laptop mode.

Your computer may be overheating due to a blockage in the ventilation. Make sure your computer is on a surface where none of the vents or fans are being blocked and that there is sufficient room for the laptop to ventilate properly.

You may have accidentally locked your screen rotation. If you swipe from right to left on the right side, you will see a screen orientation lock button that you can press to unlock it and return it to laptop mode.