Nick Stahl, star of Terminator 3, has been arrested and put in jail after getting busted by Los Angeles police this morning.   

Stahl, between going missing last May before checking into rehab, getting arrested in December and being placed on a 5150 involuntary hold at a psychiatric hospital following an undisclosed incident earlier this month, has not had the smoothest of lives.

But the roller-coaster ride isn't quite over yet -- earlier this morning, TMZ reported that the 33-year-old "Terminator 3" actor was arrested for alleged drug possession when police went to a motel to conduct a parole compliance check on someone who was with Stahl. At the Hollywood spot, LAPD not only found Stahl and three others, but they stumbled upon some crystal meth as well.

All have been taken into custody just one day after Stahl, who has battled drug addiction for years, told TMZ that his most recent stay at the hospital had been "helpful" in straightening him out.

LAPD tells us the "Terminator 3" star was arrested around 5 AM when police found him in a Hollywood motel with three other people ... they were all allegedly using meth.  

Stahl was taken into custody -- along with the other individuals.

We're told police actually went to the motel to conduct a parole compliance check on one of the people Stahl was hanging with this morning. 

Wrong place, wrong time for Stahl ... who's battled drug addiction for years. 

Just yesterday, Nick said he was happy he was placed on a 5150 hold earlier this month -- because it helped straighten him out.

The the 33-year-old actor seemed to be in higher spirits following a lifelong struggle with drugs, alcohol and personal issues, even feeling well enough to dole out advice to former teen star Amanda Bynes.

That might be a case of the blind leading the blind , however. Bynes has been involved in several high-profile incidents with the law lately and seems to be swirling downward, herself.