On my left hand, the muscles under the thumb start throbbing or twitching pretty aggressively. It doesn't hurt nor do I feel any weakness after the episode, but it's been happening way too often. Such contractions used to happen seldom and on any random body part, not particularly under the thumb. But now, it happens only under my left thumb and it causes it to bend downwards. Sometimes, if I pay attention to it, I can feel a little bit of fatigue in the target muscles. This has been happening regularly since the last 5-6 days. I showed this to an orthopediatrician on the 3rd day and he said it's nothing serious but it's still happening and I'm worried.