vehicle downshifts unexpectedly to 2nd gear

I bought my 2010 SRX used with 72K miles on Memorial Day weekend 2017. The car was relatively trouble free for the first 5K miles or so. Then I started having trouble with the brake pedal floating all the way down to the floor when I needed to stop. That ended up costing $1,800 to fix. That stung but I said to myself, "you bought a car with 70K+ miles on it, some stuff is bound to go wrong."

About a month later I was getting on the freeway first thing in the morning. As I was accelerating down the on ramp the car got up to about 40MPH and then suddenly downshifted to 2nd gear. The RPMs jumped to over 4000 and the car jerked like I had slammed on the brakes. This was pretty scary as there were cars coming up behind me at highway speed and I could not go faster than 2nd gear would allow. The car was in standard automatic mode at the time this occurred. I tried moving it over to "Sport" mode and using the shifter to try and make the car upshift. This did not work even though the indicator light on the dash showed I was now in 4th gear. Thankfully I was able to safely bring the car to a stop on the side of the freeway. I put the car in park and shut it off. After about a minute, I restarted the car, put it in drive and took off with no problems. I checked the transmission fluid and the levels were correct and there were no signs of a leak. The car was fine for awhile but did the same thing a few days later and again a couple of days after that.

Now it is a daily problem but only seems to happen in the morning or after the car has been sitting for several hours. Each time the car seems to drive fine after it is shut down and restarted. I also discovered that I can avoid the problem if I go right to manual shift mode as soon as I start the car and shift manually. Although, once the problem occurs, I can't correct it by manually shifting. The only "fix" is bringing the car to a complete stop, shutting down, and then restarting. Needless to say I have not been driving it much and the car is headed to the shop this weekend.