progressive aspect - “To sit waiting” vs. “to be sitting waiting”

• I'm sitting waiting for a bus.


• I sit waiting for a bus.

There is the situation that I'm sitting on a bench and I'm waiting for a bus in a bus station.

If I want to tell my friend that by a phone. I say "I sit waiting for a bus." It is right?

Somewhere, I have heard "I'm sitting waiting for a bus" means that I'm sitting up and down (it doesn't mean an exercise) while waiting a bus, as a bus has arrived. Therefore Someone tell me you would use I sit waiting for a bus.

Simply, I think I'm sitting + I'm waiting = I'm sitting waiting.

How are the two sentences different?

also

• I sitting waiting for a bus.


• I sitting and waiting for a bus.

differ?