It seems kind of strange that the Iberian peninsula managed to remain ununited, except for the short period before the Portuguese Restoration War, especially considering the fact that 1st of all there was a large movement for Iberian unity under Isabella and 2nd of all Portugal is surrounded on all sides by Spain.
So yeah, I am missing something here or did Spain not really care about Portugal for most of it's history?
BONUS QUESTION: Did Spain ever try to conquer bits or pieces of Portugal, or has the border remained consistent through history?
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Well, while the laws and borders of the kingdoms remained intact and separate, there was a period (called the Iberian Union these days, but that's not a historical name, it's simply one that historians have assigned to the period) between 1580 and 1640 in which the crowns of Portugal, Castile, and Aragon (the kingdom of Spain had not yet been declared) were all in personal union under one monarch - one king, three kingdoms. Spain and Portugal didn't really leave each other alone at all, and in fact were historically very friendly to each other, carving up the New World and other colonies between them.
Portugal and Castella/Spain were catholic states. The pope kept them as friendly as possible for centuries.
Plus, Portugal had (and still has) a treaty with England. Basically, for Spain to declare war and try to conquer Portugal they would be declaring war on England too.
Finally, every time Spain tried to conquer Portugal by force they were defeated. The only time they suceded was when the Spanish king had rights to the portuguese throne.