Vauxhall Zafira blows headlight bulb, overheating battery leads ???

My car seems to run fine most times but sometimes it will not start, I can drive for miles and the battery is charging up fine, everything works as it should but when I try to start it it seems like the battery is dead even though its not, the car wont start. I leave it for 10 mins and it will start again. I noted that the battery lead is very hot and also keeps blowing a headlight bulb on the passenger side, and also sometimes is irratic at idle drops to 500, then up to 1500 when sat at lights sometimes ok though ?? any ideas??