fiddle with

[GlendynaSlese]

manipulate, as in a nervous or unconscious manner

[MiguelANymn]

To manipulate an object, especially in a nervous or restless manner.

[Ernestdyday]

To adjust the position, as of an electronic device, in order to provide better reception or signal.

[LouissaRini]

To fiddle with something means to handle or manipulate it aimlessly, often in a restless or nervous manner, or to repeatedly make minor adjustments or alterations to it.