Why is my 2004 F150 XLT 4.6L occasionally overheating for no apparent reason?

What is your question?

Started to intermittently overheat (3 times/year1/2) - no odors, etc at any instance. Note: I immediately shut her down the second I see needle pegged. Was able to top off reservoir (apps gallon) within 1/2 hr each time. Have been parking on cardboard since 1st time; no evidence of leaks. Hoses I can get to seem fine. Also, heater blowing cold since roughly the same time. Picked up thermostat to change. If it recurs after, I'm at a loss. Any thoughts?rgrs.jr1@gmail.com

What makes this problem better or worse?

It occurs intermittently with no apparent cause

How long has your 2004 Ford F-150 had this problem?

Year and1/2