I think this is a battery issue but I am not sure.

Recently my F500bt has stopped coming back on when I shut my vehicle off and turn it back on a short time later. The blue light on the right side comes on but that is it. The only way I can get it to come back up is to hold the power button down for like 10 seconds then push it again and it does a full reboot.

Anyone know what might be causing this. Again, I think maybe the battery is going bad but I don't want to shell out 50 bucks for a battery if that is not the problem.

I had the identical problem as yours and the unit is only 1 month old. It is covered by an extended warranty. for short, the repair came back and it stated that nothing wrong with the unit. The DARN battery was not fully charged. I found out that it is the soft on and soft off(standby) problem that caused the battery to drain. Do a press and hold to turn the machine completely off solved the problem. Do a press and hold to turn the machine on to turn it on. Otherwise you would have the "the machine won't boot or the black screen of death problem".