I have a couple of One XLs and both have recently started playing up in the same way.
After shut down (into 'sleep' mode') by pressing the power button, they won't start up again - black screen, nothing....
Removing the SD card and reinserting forces a complete restart (yellow progress bar), but the same happens next time you turn it off and try to turn on again.
A hard reset (paperclip for 10 seconds) seems to solve it (as does paperclip and power button together for 10 seonds) but the next time the SD card is removed/reinserted, same problem.
I've tried reinstalling the navcore from scratch, rolling back to an old backup with 2012 maps, same problem. Thought briefly it was a corrupt postcode file in the 'zip' folder, but same problem even with that removed. Tried a couple of different bootloaders (5.5136, 5.5138) and navcores (9.170 and 9.530) - same problem.
It never used to happen (bl 5.5136/nc 9.170), so why's it started recently? And on both TomToms the same. It's not insurmountable, but it's bugging the hell out of me.
Please, excuse my poor English. I'm French and I never learned English at school.
What about battery life? Is the battery not too weak? Maybe is it the source of your problem...