I've had this starting problem before but now its happening again. My car clicks but it won't start, usually after running it for over 30mins and over 70mph. Does the starter overheat and not want to start?? Sometimes hot air seems to be blowing from under the dash where my legs are, is that normal?

I've changed the battery to a dry cell racing spec. I've changed the starter twice already(aftermarket). It runs good for about a month, and the same problem happens again. I also got new spark plugs and change the distributor. When i bang on the starter, it sometimes work. Pushstart always work.

Any ideas? Thanks