How to make HUD bob? (and more.)

Hey guys, have a few questions for my third person shooter.

I have a HUD, and I want to make it bob when my character moves. So here’s the questions I need answered.

How do I detect movement and set it as a variable? (Like if the character is still, set it as false, and if he’s moving, set it as true.)

How do I make the HUD bob? (I know that the branch can determine it’s activation with the variable, but how would I make it move?)

Some pictures / visuals would be appreciated.

Thanks loves.

Bob as in rocks back and forth when the character moves.