Why do I get this error message Downloading.. Do not turn off target!! and how do I fix it?

[AC Question]

Downloading... Do not turn off target!!

My note 4 has recently been randomly rebooting itself and I went into the T-Mobile store and they had fixed the problem but a couple days later it started happening again but not as often and today while I was using it the screen froze and turned off but then came back on and said "Downloading... Do not turn off target !!" and at the top of the screen it says "Could not do normal boot. ODIN MODE(HIGH SPEED)"
WHAT DO I DO?

 

[B. Diddy]

Re: Downloading... Do not turn off target!!

Welcome to Android Central! Try booting into Recovery Mode and wiping the cache partition: https://support.t-mobile.com/docs/DOC-14686