This was likely the Terminator's last chance.
The T-800 was on the verge of no longer being able to pass as human. It had to wear sunglasses to hide the loss of its eye and the damage to the flesh of its face, its eyebrows had been burned off, and the decay of its flesh was producing a strong smell that was already drawing comments from humans:
[I]n original timeline, early version of living tissue can necrotize if damaged as after being shot multiple times during the shootout in the police precinct, the original T-800's skin had a noticeably pale color and flies were sitting on its face. At this point, the janitor of the building, which the T-800 was using as a safehouse, commented on the smell of decay coming from T-800's room: "Hey, buddy, got a dead cat in there, or what?" Hence, the early version of living tissue apparently may "die" or at least undergo extensive necrosis.
— Terminator Wiki: Living tissue
The Terminator had also needed to repair damage to the mechanical components of its arm; it couldn't count on the repairs holding, or on being able to withstand additional damage. With its combat capability reduced and its effectiveness as an infiltration unit about to expire, it had this one last chance to complete its mission, and apparently it chose force over finesse as its "Hail Mary pass".
The T-800 had infrared vision capability, which it might have been using to target hot spots in the room, such as the bed that Sarah and Kyle had recently warmed. The Terminator's point of view doesn't seem to show heat — eg, the man in the parking lot at 0:31 does not show the bright and dark patches typical of an infrared view — but maybe that's what the red imagery is supposed to represent even if it isn't accurate to infrared in real life.