It should be timing chain tensioner
I dont have a V8 engine, But in 190E's, it has always been timing chain tensioners. It relaxes over night 'cools down' and when you cold start the car in the morning, it will take up to 7 seconds for it to go back to its normal tension. Meanwhile your chain is flopping around "the ratt-ratt-ratt noise" and one day it could break leaving you with a dead engine. I would replace the chain and the timing chain as well as the rails!