1st gen Tacoma starting problems

I have a 2003 Tacoma, 2.4L, automatic when it gets hot it won't start. It doesn't turn over or make any clicking sounds. After sitting with the hood up to cool down it starts right up. I've changed the starter and the main ground wire from the battery but the problem persists. Any help would be appreciated.

 

Main relay maybe? I really don't know though.

 

Thanks...I believe power only goes through the relay when the ignition is activated so it would have no cause to heat up and interrupt the power to the starter.

 

Starter relay is under the hood. Possible engine heat could be enough to effect it. When it acts up do you have power inside? Lights radio all that works? But when you go to start position nothing? Automatic or manual?
check pdf file I uploaded for diagram

 

Thanks for your reply Truck is an automatic. Because I live in Canada this is a seasonal problem I'll swap out the starter relay as it's a quick and inexpensive procedure.