Gotta remember... You're talking to a few professional screenwriters here... A scene is vastly DIFFERENT than a sequence and yet, I'm not really sure -- based on your question -- that you're really talking about a true scene or a true sequence.
Having said that...
The only time you need a new introduction line... Again, you're talking to screenwriters -- is when you INTRODUCE a new character we've not seen before.
If you're not talking about new characters -- and I don't think you are -- then the only time you begin with a NEW master scene heading is when you CHANGE location or time of day. That location can be in the same house or thousands of miles away.
Last but not least... If you're talking about continuing a scene within a specific MASTER SCENE LOCATION but are moving AROUND in that location, best to use SECONDARY LOCATION HEADINGS... These do NOT include the INT. or EXT. Just the actual location. They can be on a line all by themselves but in a spec? The read will go much better if you make a secondary heading location FLOW.
INT. HOUSE - NIGHT
A SHADOW floats from the front door into the
stops at the refrigerator -- blends in with the dark.
Refrigerator door opens -- blasts light onto a black human shape
that reaches inside -- pulls out an egg -- cracks it on the shelf
and with one hand, allows raw egg to drop inside its mouth.
Refrigerator door shuts. Darkness. The shadow continues down the
and up the stairs.
KITCHEN and HALL are SECONDARY LOCATION HEADINGS and most newbies never use them because they simply don't know what they are but writing them as in the example above makes for a much more compelling read, does not slow the reading down, and is preferable when it comes to a spec script.
Remember... Spec scripts are written to be READ and SELL the CONCEPT of a STORY to be turned into a movie. A spec script is NOT a shooting script which is what most people find online and end up reading when it comes to learning how to write a screenplay. You can learn a lot from reading shooting scripts but I highly recommend reading original spec scripts whenever possible.
Spec scripts are a combination of the two...
Now of course if none of this even comes close to answering your question? Then hopefully, you can be a little more specific... LOL.