htc one m9 stuck in loop, never makes it past optimizing apps

[AC Question]

last week purchased third party m9. hardly any new apps. ota update this weekend,now its stuck in loop, never makes it to screen past "optimizing apps" sometimes 1 of 1, sometimes more. went on for too long, got warm. never really off. willing to factory reset , but those instructions begin with it off...pulled power and let loop continue to kill it. have a slow charger seeking advice as it powers up....Also what is suggested power level to reset? thank you

 

[B. Diddy]

Welcome to Android Central! Try booting into Recovery and wiping the cache partition, which won't erase any personal data: https://support.t-mobile.com/docs/DOC-20857