Talk yourself through the problem, use something like excalidraw to visualize. Remember at a technical interview you are expected to talk while you solve, so practice that aspect instead of solving in silence
Also don’t just pick random problems, use a structured approach where you focus on one specific data structure or algorithm at a time. You can use neetcode for that
I mean talking through your solution as you brainstorm ideas and implement, about time complexity, performance implications, constraints, pros and cons, etc