Very new to forum I have been reading threads and found several interesting things. There were a couple of threads on this issue but not sure if they apply to my issue.
I have disco II '02. While driving, I will come to a stop and the "M" and "S" flash and I loose power it is very slow to accellerate. Turning off the vehicle and restarting seems to fix it for the moment. Please advise.

 

First have your battery and alternator teseted.
Is your check engine light on?

 

How many miles on your truck? As Spike mentioned, go have your battery/alternator tested, low voltage, from a failing battery or dirty cables, can cause this and will get so bad that you may not be able to drive the truck or only drive in limp mode.

 

I had the battery checked and the altenater checked last summer. They were all good. I will get those checked again. It happens more often in the warmer months.
68,000 miles.

 

It happens more often in the warmer months...like when the A/C and headlights are both on?
Alot can happen in a year.
Car batteries only last 4-5 years.

 

Get your system rechecked again cause if it isn't this than you have a major problem and you don't want to be driving the truck.