All of a sudden my 1984 308 has developed an annoying problem: On a random basis the car appears to lose power. It is as if there is bad gas, a stuck throttle etc. I was in 3rd gear today and suddenly the car seemed to die, coasted along at about 40 mph at 3500 RPM. Hit the gas and the RPM shot up to 4500 but no increase in speed. After a couple of minutes suddenly the power kicks in and the car shoots up to nearly 60 mph. Any ideas before I start trouble shooting?