Hello! I suggest first to make the trident NOT parented to the character. For example, you could parent it to the root instead. This will allow you to move it freely around, which is necessary if you want to avoid weird jiggering.
The second step Iād suggest you to take is to create a tiny bone on the trident, where you want the hand to hold it. Use this bone as Ik target for the arm which is supposed to hold it.
To adjust the rotation of the hand to match the one of the trident, you can add a transform constraint set on 100 on rotation.
This setup requires you to create movement by rotating the trident or translating it, having the hand follow it. It also has the advantage of letting your character drop it, throw it in the air, etc. Because you can set the Constraints influence to 0 to have everything controllable independently.
You can find a downloadable project with a similar setup to this here: How to make both hands stay on the weapon?
