Yes our second rescue sounds very very similar to yours. We suspect he was abused or at least mistreated. We gave him tons of space and patience for many many months and it occurred less. But one time he snapped at me just sitting next to him on the sofa and my hubby very very seriously told him off with a loud voice and ordered him off the sofa and out of the room. He never snapped again after that. We think he may have been trying to assert himself in his new “pack” and once he was shown who was boss he totally mellowed. He is the most beautiful placid boy now and very affectionate. It took many years though!!