“The doctor will be with you in just a moment.”

You're at a doctor's office to get checked up for a pain in your knee. The nurse takes you to an examining room and says:

The doctor will be with you in just a moment.

(someone) will be with you (soon)

This is a polite formal phrase often used with customers, guests, or patients to ask them to wait. Several different words can be used to mean "soon" in this phrase:

He'll be with you shortly.

I'll be with you soon.

He'll be with you in just a second.

She'll be with you in just a minute.

in just a moment

This is a polite expression to mean "soon". "Just a moment" is more polite and formal than other choices like "just a second", which sounds more casual.

"In just a moment" also sounds friendlier and sounds like a shorter time than "shortly" or "momentarily".