Renault Megane speedometer going up and down. hard to start

I dont think that the two issues are related but some Megane's suffered with the plastic speedo gear in the gearbox wearing down and causing the sympton you stated. They used a plastic spoked gear to feed the speedo and this runs against a metal one this results in the plastic wearing down and causing strange readings. Easy job to replace by your local mechanic. As for the starting problem can you elaborate?