Strangely something I can’t see
Stifles, squelches, smothers me
Stranglehold set securely
Suffocating slowly but surely
So I shiver, shudder, shake from sleep
Senses struggling but sinking deep
Such a sordid , serene sickening smile
Slips from my lips as I stare at the tile….
When I saw the title
I think you could remove all the "I" and "me" stuff, with a little rewording:
Something strange, surreptitious
Stifles, squelches, smothers, squanders
Stranglehold set securely
Suffocating slowly, surely
Shiver, shudder, shaken slumber
Senses struggle, sinking, sumberged
Such sordid, serene, sickening smile
Staring, slipping, silent style
Yeah, I sorta jacked up your rhyme scheme, but every word in there begins with an "S".
Incorporate my suggestions as you see fit (or not)!