[RedDevil]

I had this on my Nissan Almera ever when the humidity was low(ish).
I tried to solve this by touching metal while getting out of the seat, but it had an all-plastic interior and the only easy grounded metal point was a screw in the cavity of the door arm rest. I put a finger on that and immediately hurt when lifting that ever so slightly on dismount. Should have put a 100M resistor in between for gentle discharge, maybe.

The cause was indeed the seat fabric.
I sprayed it with some salt water one day, that really helped for a while. The water evaporated of course, but the remaining salt is hygroscopic which makes the fabric conduct electricity just enough to prevent static buildup.

Even so the effect is temporary so you have to respray it from time to time. You will know when to do it.

I now have a more permanent fix; I traded the Nissan for a 2011 Honda Insight.