I am sure this is getting old for people so I can only apologise, but every time I get a bit further through the maze that is imperfective/perfective I uncover a new mystery.
I constantly struggle in my brain to stop the thought that imperfective equals something that can be done at any time. For example I once used to think that maybe the fact that a button can always be pressed to reach the same effect would mean it was imperfective. However the act it is describing, the pushing of a button, denotes no flow of time during the action. So if the instructions were "push the button to open the door" I would now expect the PERFECTIVE verb "push".
Such as when a site says "как сделать салат": you can make it any time but the act of making in this case doesn't denote the flow of time and is to be completed.
Just wanted to give you that journey I've travelled in my mind so you could better understand my fear of this sentence:
"Когда не хочется выбирать между сабом и шаурмой"
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Why imperfective? The act of "selecting" seems that it is an action to be completed in this case. It is not "While I was selecting I received a phone call", where I would expect imperfective. This is "When you don't want to select", just seems that that action doesn't denote the flow of time through it, simply that you don't want to complete that action. I assume if a person said "I selected the Shawarma" it would use perfective past, so when he doesn't want to conduct this selection, why imperfective?
Sorry for the rambling, hope this is understandable