1. check outlet where you plug in your toaster with lamp or vacuum.
jiggle plug of lamp or vacuum while plugged in to check for bad outlet.

if lamp or vacuum do not work, check breaker panel/fuse box for tripped breaker/blown fuse.
if breaker/fuse okay, replace outlet.
if lamp or vacuum work okay, go to next step

2. plug toaster back into outlet, jiggle plug, then jiggle cord at plug, then jiggle cord at toaster.
this checks for intermittent power cord.

if cord okay, check that the toaster lever or toast basket are not blocked from going completely down.
might be a bit of bread, muffin, bagel that blocks the basket.

if all okay, you need other solutions.....