It's important to remember the motivation of Spain. First and foremost, they were sailing west to search for a trade route to the Indies and spices. They didn't initially set out to colonize anything, colonization arose out of opportunity.

Africa was not at all ignored: Spain and Portugal had been battling North African kingdoms for centuries as part of the Reconquista. Indeed, at times they took the battle to North Africa, occasionally holding some land there. One Portuguese King even died in battle in Morocco. But Spain and Portugal were mostly unsuccessful in these African adventures, which demonstrates that easier targets were preferable.

But you asked about Spain. Portugal for the most part already laid claim to Africa. Portugal sought out the Indies by sailing around Africa, and they turned out to be successful. If Spain wanted a piece of Africa, they would have come into direct conflict with Portugal, which wouldn't have been good for either of them. Furthermore, Spain got incredibly lucky with its conquests of the great American Empires. It is very unlikely they would have been able to replicate that success in Africa. Note that even Portugal engaged in very little ruling of Africa: they were mostly content to establish small trading posts and trade for what they need (with some minor exceptions).

Eventually, the Iberians agreed to separate spheres of influence which effectively eliminated Spain as a competitor for anything African.

Intense colonization of Africa had to wait until industrialization when the need for raw materials was much greater and European military superiority truly emerged.

Thanks a lot for the response! A mangle with Portugal would truly be dreadful for Spain.