Can I pause halfway through coking boneless shoulder?
Not exactly.

In your situation, as you're just trying to slow things down and not halt it entirely, you can turn the heat down as low as it'll go on your oven, and then when you get back, turn it back to the desired temperature.

It'll throw off the cooking time enough that you'll want to use a thermometer to check for done-ness.  (and it might finish in the time that the oven was set to low).