想起 recall, remember, pass through one's mind, 是针对过去经历的过事情的在此回想。包含一定的感情色彩，口语和书写中都可以使用，但是在写作中更常用。下面两个例句，您可以参考。 那情景使我想起了童年。The sight recalls the days of childhood to me. 他们时常想起与你共度的愉快的时光。They often remember the pleasant days they had with you. 想到 1. think of; call to mind; have at heart， 一般是指从前没有考虑的问题或者point, idea, key word 在某个瞬间想到了。 他刚刚想到一个主意。An idea has just come into his mind. 2. something that you have never expected before, we often use it with the negative forme as 没想到 in order to express the surprised (can be used for both positive thing or negative thing which are different from what you thought before, but it used more often for expressing something that made you disappointed or regret ) 我从来没有想到他回来。 I have never expected that he could come. 真没有想到！ I never think about it. *(expresssurprised feeling)The sight recalls the days of childhood to me.

按照中国人的语感， 想起：上下思维，立体式，由某个动作，某个状态，某种感受引发的想 想到：左右思维，平面式，由逻辑，推演，分析导致的想 比如： 看到美丽的女孩，偶然想起她 -----由面孔，景色，感受引发的想 遇到困难需要帮助，偶然想到她 -----由发生的一些事件，过程，理由导致的想 引发---想起 导致---想到 “偶然”表明这种“想起”/“想到”是突然的，巧合的。

基本是一样的，不必仔细研究。 如果一定要区分的话， 如果你偶尔思念她，包含感情的，就说：我偶尔想起她。有一点意味深长的感觉, maybe a little bit moved, emotional, or sentimental... 想到她，更像是一种突然性想起, without many feelings.