Can anyone help

Hello all first time post,I,m driving a 2008 1.9.td octavia with 85000 miles and for the 3rd time last night my engine revs rose to around 1000rpm and could hear a strange noise from engine area which got louder as i accelerated.I switched off engine and restarted and revs were normal and noise gone.The noise sounded like a dry clicking (if that makes any sense).Due to traffic conditions I could not get out to investigate.Clutch and timing belt both replaced recently.If it happens again soon and I get the chance to have a look and narrow it down I`ll keep you updated but if anyone has any ideas they would be welcomed.