Z28NEVALATE

I have a completely stock dd 98 z28 a4 with 190k miles that was driving fine until the other day. I was cruising around town and all of a sudden my poor baby started missing. I drove to a local parking lot about 1 mile away to park the car and noticed a small amount of cloudy whitish-blue smoke from the tailpipes. I left the car there and came back later to see about it. I attempted to crank it and there was a loud noise when I turned the motor over (as if something broke). I left and came back tow it home but decided to try and crank it and it started right up but was still missing and had the lil smoke still. I drove home driving 35 mph and the temp never ran hot and I had oil pressure according to the gauges. I parked the car and didn't drive it anymore afterwards. I tried to crank it today and it the motor is froze somewhat. (my battery is fine and starter is also, got the battery charged the night before because while trying to crank it it sounded as if it was dead). I later turned the engine manual through the crank to see if the motor was locked up and went to start is again and it turned over somewhat then began to freeze again. I repeated this about three times and it finally crank but it sounded like the lifters or valves (rattling) were about to jump off of my motor! That noise (lifters or something like the valves) later calmed down after being crank for maybe a minute and the engine cut off and I left it as it was.
What could be wrong??

Please help!!