2004 Toyota Solara, unsure of what's wrong with my car!!!!! Tranny/Electrical??

My 2004 Solara has been operating fine, I drove to LA over the grapvine
doing about 80 mph the whole way, a total of 130 miles without any issues.
Once heading back north entering onto the 405 with heavy traffic my dash
stops working, RPM's, Speedometer both dropped to 0, check engine,
brake lights begin flashing, as well as losing power to accelerate. Needless
to say I freaked out!!! The car regained power as I was veering over to exit
the highway to figure out what to do. It kept going in and out every few
minutes, until I could pull over to safety, Thankfully I was able to do so. We
checked the transmission fluid it was full, my car can operate in automatic
or shift manually (up/down shift), we figured out that we could use the
manual shifting & have no issues whatsoever, other than the check engine
light remaining on. So we safely made it home, after a few hours of being
home the check engine light is off & I'm able to use automatic shifting
without everything quitting again. What could possibly be going on with my
car?