"Deadliest Catch" star Elliott Neese is an unstable ticking time bomb waiting to explode ... so says his baby mama who just got a restraining order against the reality star.

According to court docs filed in Alaska obtained by TMZ, Neese -- the captain of the F/V Ramblin' Rose -- has been on bad terms with his baby mama Valerie Gunderson for a while ... and now she believes there are signs he could "snap" on her at any moment.

One of the BIGGEST signs, Valerie alleges ... is that Elliott has been drinking, possibly using drugs and harassing her through the phone.

In fact, Valerie claims on Feb 13 ... Elliott called her 38 TIMES and sent 15 texts her way in less than an hour ... when she refused to talk to him.  One month before that, Valerie claims he called her 54 TIMES in one night.

Valerie claims Elliott also called her mother and told her, "If I can't have [Valerie] nobody can."

Valerie claims Elliott has a history of domestic violence -- smashing her belongings in 2010 and attacking her in 2006 -- and she doesn't want to be a victim again.

The judge felt Valerie's fears are legit -- and has issued a temporary restraining order against Neese ... banning him from calling Valerie or contacting her in any way.

We attempted to contact Elliott for comment ... but we're told he's currently out fishing and could not be reached.