DON'T BE, says legendary Oakland rapper Too Short -- cause Beast Mode was just gettin' down the only way he knows how.

"It's pretty normal where we're from," Short told us outside Catch in WeHo. "That's how we all dance."

Of course, Marshawn's from Oakland ... so when Vell and DJ Mustard's "Oakland" track hit during a timeout in the Raiders' blowout, he had to let it flow.

Some Jets players reportedly said Lynch's beast moves were demoralizing -- and Short definitely agrees.