So it started with the belt making noises and me putting off the simple task of adding tension. Yesterday, out of nowhere, the engine began vibrating so bad the car shook. I drove it home and parked it. It feels like driving over cobblestone roads. Today I start it up to take a look at what I can diagnose and the oil light comes on. Yes, it is at the proper level and has been kept that way. So.... Where do I start? What can I eliminate immediately to begin to isolate the problem? What should I focus on?