Dps 3 belt slippage

Is it normal to assist the dps turntable to spin when it is cold? I find I need to give the platter a push or else the belt just slips on the pulley. This is only required on the first play in a session.

Or does it mean I need a new belt?

Thanks for any advice
When my DPS 3 does this (it's common), I get a new belt which fixes the problem.
Thanks. I have cleaned the belt which has fixed the problem, but will order a new belt anyway for it's about 3 years old.