Let’s talk about vibrato.
In order to do vibrato well, it’s important to understand what vibrato actually is.
Vibrato is a small repeating bend that bends to the same pitch, releases to the same pitch and pulses at the same rhythm.
In order to improve your vibrato, you can practice it to a metronome.
Start with your metronome at a slow tempo, on the 1st beat hold the note, on the & of the 1st beat apply a small bend, on the 2nd beat release the bend to the original pitch, on the & of the 2nd beat reapply the bend, on the 3rd beat release the bend, on the & of the 3rd beat reapply the bend, on the 4th beat release the bend, on the & of the 4th beat reapply the bend.
Once you become comfortable with this exercise using 8th notes, you can take it up to 16th notes.