Advice wanted. Why does my cat jump out of his skin?

Hi all,

I've recently adopted an 8 year old ginger tom from the rescue centre. We don't know much of his history except for that his old owner passed away and no one else in the family was willing to take him.

We've have had him about 8 weeks and he does have some strange behaviour issues like being a little bit scratchy and bitey, but this mostly seems to be misdirected play and he has been improving whilst we try to be understanding and accommodating. Apart from that he's a lovely cat. He's quite clingy and always wants to know what you're up to!

Anyways, on to the question. Every know and then, when he is relaxing, not even asleep sometimes. He will launch him self out of his skin! It's obviously a fear reaction but I have no idea what sets him off. He recovers from this almost immediately and usually just starts relaxing again.

I wondered if anyone had any experience or advice of a cat that does this? I've had cats my whole life but I have never seen one do this before.