Hello members - i recently purchased my WRX 2.5.. 2006, does this happen to anyone else car starts fine - but after 2,3 seconds she develops this low knock noise then goes away after 10 seconds or so.. should I be worried - she’s the correct oil level etc..

Its hard to say - is it a knock or a tapping noise?
Top of the engine or lower down?

When the engine oil is due to be changed I would use a quality (OE spec) oil filter and it would help to flush the engine (an additive or detergent that breaks down carbon build up) and then replace the oil with a quality oil (Castrol, etc)