1994 Buick Park Avenue car problems.

Ohk so, my car just recently started acting Up. When I go to get on the highway or freeway the car takes a while to get up to. Speed, but as she's getting up to speed the rpm is at 3-3.5, than she'll catch up to herself and rpm drops to 1-1.5. If I take my foot off the gas the rpm drops all the way down and than comes back up. Also, my check engine light and change oil light come on and off just did an oil change not even a month ago, less than 600 miles ago. She also shuts off sometimes unannounced. My oil level, battery level, and temperature gauge all drop to zero and their lights come on and car stalls. Happens about once a day or every other day. Sometimes if I drive somewhere shut her off run in and run out she won't start. I wait a little while 15-30 mins and she starts. Almost if she's overheating but my coolant is full temp gauge reads normal. Lastly if I let her sit for longer than 4-6 hours when I start her this thick white grey smoke comes out the exhaust. Please help all you can thank you. !