On 4-5 occasions over the past 3 months I have experienced an issue where the transmission doesn't shift and stays in 1st or 2nd(not sure) I see in the manual you can't check the level as it's sealed with no dip stick. After it does it, I park it and the next time, maybe later the same day orthe next anyway, it shifts fine until it happens againin a few weeks. The first couple of times it was very cold outside so I thought it might be related to a cold catalytic converter but the last couple of times it was warm. Does this suggest an upcoming implosion and any suggestions on heading it off?