Try sitting in the Egyptian pose (on a chair), standing or walking meditation.
Try kneeling with pillows on your ankles.
Yoga asana ARE meditative postures.

If determined to continue sitting on the floor ...
Start with prostrations to the Buddha, this will warm you up a bit.

Zenith advice
https://youtu.be/1_djWyC1-_4

You might also find my meditation notes useful
https://cundi.weebly.com/meditation.html