Lux
these symptoms can be cause by a bad intank fuel pump, if have that checked ive seen alot of volvo run with those pumps out and some that just dont, id check that which will require that the fuel sending unit be pulled from the tank as they are all attached, which means it can be cleaned while out of the tank so you can feal relived its probly not bad once you have it cleaned. if this is only happining at the 1/4 tank lvl thats exactly where id start out.