04 Quest Engine noise at startup

Hi,

I just bought an 2004 Nissan Quest 3.5 SE with 150 k on it. When first looked at it before I bought it I did not notice any noise but next day when I had it in the morning it made a noise from the engine that lasted 1 minute then gradually disappeared. I checked the oil level and it is good.
Just wondering if this is pointing to a major problem or it's normal for those kind of vans. What should I check or may be ask my mechanic to check?

Any help or suggestion I highly appreciate.

Thanks