怎 sets 乍 (sudden) on the heart 心: the jolt of surprise that makes you ask 'how?!'. A question word with the emotion still inside it.
怎 powers the how-questions: 怎么 (how), 怎么样 (how about it? how was it?), 怎么了 (what's wrong?). 怎么办 — 'how to handle it?!' — is the national phrase for any predicament, from lost keys to life crises. You can hear the startled heart in every use: something happened, and now the speaker needs a method.
A sudden 乍 jolt to the heart 心 — HOW?!
怎么办?! ('what to do?!') is so universal that it's often the first 'emotional' Chinese a learner acquires.