I had my oil changed a couple weeks ago due to it being black and ever since then my oil pressure gauge has been erratic. It sits up high (second needle to the top red) when the car is started and then slowly goes down. During regular driving, it'll sit anywhere from the middle to near the top, but when sitting in traffic or not touching the throttle, it'll go right down to the first needle. A few times (about four or five times now) it has dropped all the way to the red and I've had the beep warning. The only way I've found to fix this is to give it light throttle to bring the pressure up over the red.

Is this a sender, a switch, or could the oil change just have been done wrong? I find it hard to believe an electrical component that worked fine before would just die randomly after an oil change.

Sounds to me as though your oil pump relief spring is at fault, or your oil pump itself. How long between oil changes? If it has been left for a looonng time, dirt and rubbish may have clogged up the relief spring in the pump, and/or worn the pump itself. Low oil pressure often means stuffed big ends too......

It could be the sender switch, they're known to play up and give those symptoms. Maybe clean it or try a spare one they're really easy tro to swap over