quick question

[1974ChevyC10]

i just got to work after grabbing some food.when i left wendy's at first when i hit the key my starter would make this noise the best way i can describe it is freewheeling.i hit the key and the starter would freewheel and make this clicking/slight grinding noise.then i put the shifter down in L1 and went backwards slowly into each gear and the truck started.then i drove to work and park.check to see if it would do it again and now all it does it click-the starter armature hitting the flywheel but it wont start.i do have headers,it is kinda hot here today its 96 degrees with approx 26% humidity.could it just be my starter is just hot and needs to cool off or is something else going on here which i hope there isnt because i dont want to be stranded at midnite after i get off work im a 30 minute drive from my house.please help.thanks