I worked for someone as a construction worker & received a 1099-MISC. I didn't start or stop residential construction in 2019 on my own. So how do I respond to that Q?

If you are working on your own as a contractor and this is how you make your living, you can just indicate that you neither started nor stopped working in this field in 2019.  

This means that you are in the business of construction on your own.  The person who issued you the 1099 did not pay any Social Security taxes or Medicare taxes on your behalf.  As such, you are treated as if you are self-employed.  

Since you are working as an independent contractor, you are subject to Self-Employments taxes but are also able to deduct any business expenses on Form Schedule C.

Attached is some additional information to assist you in reporting your Self-employment activity.

Self employment taxes guide