My boyfriend has a chihuahua/terrier mix, he's about 7-8 years old. Lately he's been getting small seizures. It starts first by the way he walks, his muscles and bones seem weak and can't seem to support his body, tail between his legs. Then he lays down and shakes, and muscles seem to contrapt a little. He doesn't moan or cry, and after a few minutes it goes away. What is this problem? Is there any way to help??