Wells/Pumps

My well pump (Gould jet pump) has recently started running in short spurts, say 30 seconds at a time. When the pump first kicks on, the pressure jumps immediately from 35 to 45 psi, runs for about 30 seconds then shuts off. About 20 to 30 seconds later, the pump kicks back on, and the cycle repeats, for as long as water is being used. The pump and tank are about 3 yrs old, and were working properly until recently.How do I go about resetting the air pressure in the tank (drain tank, pressurize to 30 psi, then fill tank??).Ive done it once before on the advice of a plumber I knew, but I dont remember the procedure. HELP!! Thanks!