99 regal dash lights intermittent

I have a 99 regal sc. About a week ago I was driving to work the dash warning lights flashed briefly then went off. This seems to happen either early in the morning on my way to work or in the evening when it is dark out. I took it by my mechanic he ran code chec on it nothing came up. He told me to keep track of when it occurs. It did nothing for a few days after that. Then it would do it again. I replaced the battery as I have only owned the car for over a year and did not know how old it was. That was done yesterday. nothing like this has occured before.. After the battery was done. I drove home everything was fine. I went to the store started to make a right with the turn signal the dash lights flashed and died. I started it and everything seemed ok. This morning I had been driving to work stopped at an intersection to make a left turn the dash lights dimmed and flashed and the car died. I started it up it did it again. Then It all worked fine. I made other left turns and nothing. I am dropping the car off at my mechanic tomorrow. Any suggestions I should try before that. I have read in some of the other posts about the bcm under the drivers dash. I have not removed the cover to see if maybe something is loose there. Any suggestions would be helpful. Thank you

The problem with intermitent electrical is that it is like finding a needle in a haystack. From what you described it sound like there is possibly wires in the steering column that are shorting out. Sorry I could not be more helpful.
I would be curious to know what your mechanic finds though.

A common problem on these cars is the ignition switch/harness assembly. The contacts start arcing and cause all sorts of random electrical gremlins in the ignition switch controlled circuits. Common other issues are HVAC problems, DIC flashing/blinking, IP issues, etc...