My new 2005 e320 cdi... intermittent loss of power acceleration?

[wallbenz]

I took it out for about 4th time....
Drove fine after replacement of thermostat

Got temp up to normal

Mpg increased from 33 to 36

Drove 20 miles highway

Trip back
Started up and felt immediate loss of pickup
Felt like ny 84 sd

Drove 20 miles back home... same
Got off express way... pulled over... and restarted car

Car was back to.normal ... power / acceleration

Mpg falling back to 33 during power loss

Any ideas on what that was all about?????

Almost felt like turbo stopped working

And started working again after restart???

Help!!!