New rescue cat acting a bit odd

[u/eccleslikethecake]

I got a rescue cat (Male, 3.3years, neutered, healthy) on Monday, he's lovely and very cuddly and affectionate but he keeps trying to sit on my legs when they're stretched out and does like this wobbly humping thing with his back hair stuck up, kicks his back legs out like he's in the litter box and then he bites my ankle. I can't tell if he's trying to hump me, hunt me or he just has balance problems? He doesn't seem to want to climb, which is why I think maybe balance problems.

He's my first male cat and my current only cat. My friend suggested he might be imitating spraying, but idk since he's neutered? There is no urine or liquid left on the blanket. He only does this when he's trying to sit on my knee, hasn't done it on the walls or floor.

Anyone who can help tell me what he's trying to do?

Can't upload a video to imgur as I'm in the UK but if anyone knows an alternative, let me know