So I went out and got a tidy track and tidy wheel cleaner.  Last year I had no problem with keeping my engines and cars on the rails.  All of the sudden 2 of my trains engines keep derailing and not always in the same place.  It could past that spot 3x or on the first time and then derail.  I checked all of my connections between sections and no issues.  Got re-railers every 6' which do not help and are sometimes the point of derailing. 

On a separate issue my trains also just suddenly stop and a very light finger push will start them again (DC & DCC).

I always get great answers here and would like to thank you all for your support up front.  Because sometimes I get so involved with your answers and fixes I forget to write back right away (apologies). :-)

It seems that different manufacturers give their engines different polarity.  Which makes it difficult with turnouts.  As it hits the new section of track on the turnout it of course reverses.
Other than switching wires on an engines polarity, is there another way to make it a continuous run without reversing?    
Thnx!!!

So I bought some turnouts for my layout.  #6's cause I use large engines.  I have tried it with both the frog wire (underneath) connected and disconnected.  And the same thing happens on both left and right turnouts.  When going straight and not taking the turnout; as soon as the engine passes the frog it stops.  Checking continuity the inside track has none past the frog.  And one of my switches for changing direction burnt out.  These are DC switches running on AC power, on an HO layout.     Any ideas other than adding another power rail on that section of track?     And why would a switch burnout that is less than 2 months old?  Thanks up front.