Hello, I am having some issues with my 03.

Hello, I am having some issues with my 03 Saturn Ion. Last week while my husband was driving the car it lost power and did not accelerate after stopping at a red light. We thought maybe the transmission, but it is not having any troubles shifting gears. Took it to our mechanic who got in contact with a saturn engineer who suggested a new battery. It was due for a new battery, and it ran fine for two days. However, today the same thing happened. First the coolant light came on, and then went off. After driving 15 miles or so the engine light came on, and stalled again. We were able to pull over and after shutting it off, and starting it up again it ran fine with no problem. We also had the fuel pump and line replaced 2 months ago. We took it on a 600 mile round trip a few weeks ago and thinking back I remember the fan running very loud when we reached our destination and turned the car off. Being that is a Sunday I cannot call the shop until morning, and I don't have any codes that they may have read. I have been doing some research and seems there could be a number of reasons why this is happening. Hoping with this info you could narrow it down for me. Thanks!