fiddle around

fiddle - a violin 

fiddle around - to waste time, to pass time doing unimportant things

"He is a night person, and he loves to fiddle around late at night when everyone has gone to sleep."

"My brother is outside fiddling around with his car engine. He should stop fiddling around and go out and get a real job."

"Acer has unveiled a PC Revo whose parts are designed to be fitted together like building blocks. Customers no longer need to crack open the case and fiddle around with cables and wires."