I remember two scenes and a bit of the story from a movie I saw on TV in the late 90's or early 2000's and would like to know what that movie was. I'm not sure if I remember the scenes correctly and I'm not fully sure if they are from the same movie.

If I remember correctly the story involved some stones probably from the outer space that mutated people into monsters though still looking and some time after the mutation turning back to acting more like normal people but not back to humans. Though I'm not sure at all because I remember not watching the full movie only few parts of it.

A scene near at the start of the film had two people driving on a highway. The other person started feeling sick and they stopped at a gas station. The person feeling sick started going mad and sticking his head between some shelves and turned into a monster.

The other scene from near the end of the movie had a woman and a mutated man having a conversation. At some point the man tricked and forced the woman to hold a stone in her hand so that would mutate her too.

I'll give this a try:

Invasion (1997 TV miniseries)
Aka Robin Cook's Invasion
Starring Luke Perry, Kim Cattrall, Rebecca Gayheart, Jon Polito, Neal McDonough, Rosanna DeSoto, Castulo Guerra, Chuck McCann
IMDb synopsis:
Small rocks fall from the sky which, when touched, trigger a latent virus that has always existed in humans and begins mutating them into an alien species. Taking advantage of its hive mentality, the aliens are absolutely dedicated to transforming every human on Earth and do so with alarming swiftness. Only a small group of humans remain who have the medical knowledge to devise antibodies to reverse the effects of the virus.

Synopsis 2:
After what appears to be a meteor shower, a young man is "stung" by a small rock. The rock is actually a tiny UFO which infects humans with a strange virus that begins with a mild flu. Victims then return to normal health but develop cold, emotionless personalities. The first victim, Beau, has a different reaction: He becomes a power-mad egomaniac and founds an institute for the alleged betterment of mankind, then his appearance changes to that of an alien. His girlfriend, Casey, and a small group who have avoided the virus, search for an antidote that will end the extraterrestrial takeover. When Casey is stung, they must race the clock before her metamorphosis begins and the extraterrestrials can accomplish their mission.

Invasion (TV Movie 1997) - IMDb