e36 323i with a scorpian exhaust light smoke

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Hi all i recently purchased a bmw e36 323 which had done 150,000 which for bm's i think is nothing, the oil and water are spot on never drop and temperatures are normal, however ive recently noticed light smoke only sometimes coming through the exhaust nothing major at all it then goes away after a few seconds of start up any ideas if this is a fault indication or nothing to worry about if any one knows any thing like this please can you post thank you in advance and happy new year