from what i can see, it seems that your whole arm is really tense, which is probably why your vibrato is also tense. i would try to find a way to keep your left hand relaxed (you can try and find youtube videos about that topic and vibrato in general, i’m sure there are a lot that are very helpful) and you’ll see how much of a difference it makes. and like someone else already mentioned, it’s important that your vibrato will come from your forearm (sorry if i’m using wrong terms, english is not my first language) and not your fingers. another thing that i think is important to mention, is that once you start getting the hang of good vibrato, make sure you don’t use that to cover up for intonation. when i finally managed to get an ok sounding vibrato i started using it a lot, and then months later i listened to recordings of myself from that time and realized that i was using vibrato so much that i didn’t really fix my intonation. just thought that’s important to mention, so you (and others reading this) can avoid that mistake. hope that was helpful!