Ray McDonald -- ARRESTED AGAIN ... At Sandwich Shop

Ray McDonald has just been arrested AGAIN -- this time, cops say he violated his restraining order ... and was taken into custody at a Togo's sandwich shop.

According to police, the NFL player had been ordered to stay away from the residence where his ex-fiancee has been staying in Santa Clara, CA after Monday's domestic violence arrest.

As we previously reported, McDonald was accused of attacking his baby mama while she was holding her child early Monday morning.

But cops say he returned to the scene of the alleged crime Wednesday afternoon -- but quickly left ... and went to the Togo's, where cops found him and arrested him around 5:35 PM.

Cops say he was arrested without incident and taken to a nearby jail where he was booked.