depending on your strenght , and some perks every character has a limit of weight they can
carry , if it says you cannot run it means you have surp***ed your limit , therefore you
need to drop some of your equipment or anything that has weight in order for your total
weight carried drops below or right on the limit , having a companion also helps to carry
some items. Once you carry less or exactly the amount of weight permitted depending on
your strenght and some perks then you will be able to run again.....

if you have a house(megaton or tenpenny tower)
put the items you dont need in the lockers and containers and drop stuff you dont need!!

Its because you have too much weight. things like armor are extremely heavy.
Putting Them In Your Home Is A Good Way.

Use buffout to bring ur str up and use armors that bing str up.. For more info message
spinachehead95

I meant to say spinachHead95

you cant