I used to be unable to hold my right hand still in the air without slight tremors, and I noticed how it went away some months after I quit playing this one mmo with excessive clicking. Phlebotomy is so much easier with a calm hand. Maybe the toy would help if it's hands-free?
Adding this fun read because I know hands do get numb from holding strongly vibrating things for excessive periods of time: https://www.cdc.gov/niosh/docs/83-110/default.html
Moreso in your jerking hand, or both? Not that I have any qualifications to answer further -- better to check with your doctor how serious it is.
What's native call recording? Like call recording with the default phone app?
I use ACR Phone by "NLL APPS" in the play store. They have you download their app store to download their ACR Helper app to run in the background, which allows the recording. But the quality of the other end's sound is based on your in-call volume. So after the call starts, I have to ensure the volume is turned all the way up. It doesn't have to be on speaker.
I haven't needed to root, or else I'd have trouble getting on certain mobile games that check my phone for root.