Strange odor when 1st turning on water

I have a strange problem in that when I run first run my bathroom sink there is an odor that comes from it. However it's not the water as that taste fine, plus it does not happen on other sinks or the tub. It seems to only happen during the first minute or so and then it;s OK. Any ideas of what to do.

Thanks in advance John

Is the smell coming from the tap or the drain?

Check the trap under the sink. make sure it does not have a leak that causes it to go dry. you may be smelling sewer gas displaced by the initial flow of water. Is there any oder before you turn on the sink.

Is the odor organic or chemical like? Try running the water with the drain closed. do you still smell it. This test should help discriminate if it is from the water or the drain.