Nissan xtrail 2003 hardststart and Loss of power

Hi
My nissan xtrail 2003 model has challenges with
the following;
1. Hard start, I always have a challenge of
headstart where by whenever am starting the car,
its take long to pick like it has no fuel. I have
changed the spark plugs and as well did service.
2. Loss of strength; whenever am on high way
driving at speed from 40 to 50 to 60, the car
shakes as vibrating and then stabilizes af 60 .
At times when I try to step on it while over taking,
the car shakes as struggling.
Changed all fuel and cleaned the tank as well did
full service but still no solution for all this


Kindly advise