Sounds like a fuel supply problem.
Could be
1) blocked fuel filter in tank
2) crack or hole in the line between the filter & carb
3) collapsed tube above from using ethanol fuel or some bad fuel ( fuel is not petrol as we used to know it )
4) blockage in the impulse feed from the crank case to the diaphram pump ( or leakage via loose or broken or dried out gasket )
5) torn or hardened pump diaphram
6) blocked passage in the fuel pump section of the carb
7) blocked screen in the carb
8) sticking needle
9) blocked main jet.
10) loose carb mounting bolts
11) blocked petrol tank breather
12) blocked muffler
Think thats the lot.
Start with the easy bits first like loosening the fuel cap, tightening the mounting screws ( carefully ) and removing the muffler
From here on in it is a matter of how much time / money you have and your mechanical competence .
Easiest thing is to swap out the carb, if no better then replace the fuel lines & filter, do all of them.
The retail cost of a carb rebuild kit is about 2/3 the cost of a new carb and rebuilding requires surgical levels of cleaness, the holes are tiny and the slightets amout of dust renders the job useless.
I rarely recommend rebuilding now that the price of replacements has dropped like a lead balloon
