Pull your current relay and check for corrosion on the posts. My OVP in my e320 caused the same symptoms you are describing. I bought a new ovp but its still in the box as cleaning the old relay with a wire brush did the trick.

__________________

77' 300D, "Cartman" SOLD @ 150K (didn't know what I had)
83' 300SD, "The Superdon" 325k+ @ 28mpg
95 E320 wagon, "Millennium Falcon" 231k+ @ 24 Mpg
95 E300D, "Sherley" 308k @ 33.69 Mpg, currently anticipating a head
99 Suzuki Intruder "Trudy" @ 45 mpg