Engine Failing? 2007 Prius

My Prius has been acting strangely. It started with the engine not staring right away one day after I pushed the button. Instead the check engine light came on and it sounded like it was straining and then the engine started up and the light went off.

I never changed the oil since I got it, it had been about 6k since then, so I got an oil change. Engine seems to turn on more when idle like at red lights.

When I turn off the car, sometimes it turns right back on with the check engine light coming on. When I hit the button again it turns off. Next time I turn it on, no check engine light.

I did check the codes when this happened but my small reader didn't pick up any codes. I may need to try techstream next time it happens in case it can detect more.

Not really sure if I'm just hitting the button too fast, hard, etc. sometimes or what's up with it. Other times it runs just fine. Seems to do worse in the heat but may be my imagination.

Possibly unrelated, had my traction light come on and car be a little swervy for first time lately, three times now. One on gravely road, another on a turn, and one on windy roads. Could just be coincidental timing and it works fine?

Any help would be appreciated!

 

I just checked with Techstream, no codes.

 

I'm not sure. What should I do next? Besides forking over my arms and legs to a mechanic if I can help it.

 

I've been making sure to start and stop it properly but it still happens. It has become more frequent. On turning off, dash turns off and then everything comes back on, all the lights, til I hit the start button again and it goes into ready mode. Sometimes the check engine light stays on until I turn it off and on. Once, it stayed on again til I did it again. Have not checked with Techstream again yet. On turning on, sometimes check engine light comes on until engine rumbles to life.

At lower speeds it feels like engine is more rumbly lately, turning on and off more frequently perhaps or struggling to change gears I'm not sure.

I checked the voltage of the 12v today when it hadn't been running for a day or so, it ready 12.56V. I checked it because my car died overnight the other day. Well, at least it was unresponsive with no dash lights. Unplugged and replugged in 12v and it turned on again.

How do I check main battery? My console screen is burnt out on the Prius so I can't do it through there.

Wish I knew what was going on.

 

Only what I described in my other recent comment. Is there something I should check?