The check engine light can also mean you have a transmission problem which would be my guess. You need to have the ECU scanned with an OBD2 scan tool. This will bring up the code that has been stored by the computer. It could be minor and could be serious so do not ignore this or you may end up with a very expensive transmission repair. A professional can take the code and know where to look for the problem. Transmission repair needs to be done by a pro, as this is not a DIY repair. Stay away from chain transmission shops. Seek a trusted pro that family and friends recommend or take it to the dealer who sold you the car. Good luck and I hope it is nothing serious.

There are many probable causes for this problem, you said checked the transmission fluid and it looked OK, first thing you should do is to make sure the fluid quality and level is good if positive and still having problems I recommend changing the fluid and fluid filter. If the problem still persists, then it might be caused by Transmission Control Module, a sensor or solenoid, or the circuit itself ( you mentioned the flashing engine light, the problem can be caused by a faulty sensor or circuitry). if the first simple remedy doesn't work I recommend taking the car to a professional to have a look at the probable problematic parts I mentioned. Have a look at it and let me know if you need more advice. Best

Remove your cats, they have melted close ie your exhaust is plugged up