5:57 PM PT -- Lamar just apologized for making "a bad decision" ... and says he'll "set a better example going forward."

Here's Baltimore Ravens superstar QB Lamar Jackson apparently breaking some laws ... speeding at 105 MPH -- all while holding his phone and recording!

C'mon man -- BE SAFE!!!

LJ posted the (not so smart) footage on his Instagram Story Tuesday ... presumably to show off his icy bracelet and fancy Mercedes.

The problem? You can see in the vid, the speedometer is PASSING 105 MPH ... with his phone locked in one of his hands.

Yeah, ain't exactly a look the Ravens want to see.

Plus, there's a seat belt light on the dashboard, which shows someone in the car ain't buckled up. It seems Lamar's alone in the car. We're HOPING it's a mistake and he's buckled up for safety.

What makes things even tougher for the Ravens to swallow? They've had an up-and-down offseason so far, losing studs like Terrell Suggs and Eric Weddle -- and Jackson also posted he isn't happy about that.

"Lol I wish we could've kept everyone," Jackson said ... "us players have 0 say so."

We've reached out to the Ravens for comment on Lamar's vids ... but so far, no word back yet.