YNW Melly's Mother Wants Sheriff Investigated After Rapper's IG Posts

YNW Melly says he fears for his life inside Broward County jail, and his mother is taking him at his word ... and demanding immediate action before there's a turn for the worse.

Jamie Demons-King says she's tried to get some relief from the judge in Melly's case, but is taking action into her own hands now by bringing the matter straight to the county commissioner.

The "Murder on My Mind" rapper called out specific guards in 2 IG posts this week, accusing them of threatening to beat him up and isolate him from the other inmates.

Melly also says his phone privileges have been revoked and feels like he has a target on his back. Jamie tells us she's feeling helpless over her son's predicament.

She says Christmas Day is her birthday and all she wants for a gift would be to talk to Melly ... but she's not certain it's going to happen.

We reached out to the Broward Co. Sheriff's Office, but haven't heard back yet.