Alright I just had this problem with my 3ds new xl, I've been letting it sit after playing around with it for a bit seeing what I could do, noticed it took unusually long to hard off when i held the power button. Today I turned it on and noticed the red blinking light, it to was blinking slowly. So after looking threw these I chose the simplest one, and huh. I just left it on for like 5-10 minutes while having a smoke. I seem to have caused some sorta error in the bootup that just caused it to boot really slowly, I imagine an older model woulda been even longer. It seems to have worked through whatever error that was filling the cpu now that its got to the homescreen. I also know it happened right after it was charging and we flicked a bunch of breakers on and off a few times, we were checking wiring. Oh and my sd is 256 gigs I could see that causing the occasional problem on boot. Alot of these other solutions like taking out your battery, performing different kinds of resets for clearing you're caches....