I had a golf come to me with the same problem a few weeks back, turned out the cam timing was out slightly, and 2 of the 3 plastic rings/seals on the cam adjuster were broken from where they had put it back on.
I recommend to always change the rings/seals when doing the timing chain as they seem to go extremely brittle over time. Especially for the sake of the £18 or so that they cost.
Car ran perfectly after having them replaced and the timing adjusted, hope this helps.
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