lookingformore

I have a 2004 Malibu Classic - and it's been having an issue on and off, for over a year. Both my dad and my brother, wasn't sure what was causing it. On a side note, I did replace the exhaust on it, so I don't think it's due to that.
I've had issues with pulling out to make a turn, and loss of power, lights flashing on the dash, getting up to 2-4mph,, getting off on a side street. If I would shut the car off, and restart, it would clear it. I had that happen two times and no more.
What happens now, and it used to infrequently.. I would start my car and it would do rough vibrating idling. If I shut the car off and restart it, it would clear it up. Now I'm getting those more often, and yesterday it was that and something else.
I went out to start the car and it almost sounded like a battery issue, with cranking and not starting for a few seconds. I tried again and it wouldn't start, but left the key in that position and the car tried starting again,without me touching the key.
It was rough idling ,so shut the car off. I tried again and it started, and I drove to a post office, where my son sat in the car while it ran, while I went and mailed something. When I came out, he told me that the car started vibrating a lot, but stopped.
I drove home as I didn't want to take a chance on it.
I just went out and started the car - and it started right up.

Now, can someone PLEASE help me with this? I'm not near family, and my Dad (my goto mechanic) passed away in April.

I've used bottles of Sea Foam (my brother said to) and it doesn't seem to help.

Thank you in advance!