Shutting off randomly?

My vehicle has had the fuel pump replaced, catalytic converter, the O2 sensor changed, spark plugs, and the computer system board under the hood on the right. Not sure what it's called. It has constant oil changes, and the gas tank is at least half full all the time. With that said my car will randomly shut off. Almost always when I'm stopping or have just turned. I haven't seen what the gauges do when it shuts off, but all my lights come on but don't stay on. It always restarts after about 30 seconds or so. I haven't noticed any smells, leaks or odd noises. I'm at a loss trying to figure it out. The only thing I can think of is either my battery. It sits in the space for it, but it can move a bit from hard braking. There's a piece of wood there to help keep it in place. The terminals are clean and tight. My other thought is a timing belt or alternator, but I don't know for sure. Any thoughts would be appreciated. I use my car every day for work and am one step away from a massive anxiety attack if I can't figure this out and am also not made of money. Please help my sanity. Thank you.