Where are you going?

[Silverobama]

When I walk on the street, I can see people using their phones to find a place. I am a bit warm-hearted so I usually walk up to them to say "Where are you going?".

Is this expression natural?

 

[emsr2d2]

When I walk on the street I'm walking around outside, I can often see people using their phones to find a place get directions. I am a bit quite/fairly warm-hearted friendly/helpful so I usually walk up to them to and say "Where are you going?" no full stop here

Is this expression natural?

Note my changes above. Your italic sentence is grammatically correct but it's a bit direct (almost aggressive) for the situation! Try something like these:

Hi. Do you need any help?
Hi. Can I help you find somewhere?
Hi. Are you lost?

If a random stranger walked up to me in the street and said "Where are you going?" with no greeting or pre-amble, I'd probably say "None of your business" and walk away as fast as possible.