2003 Chrysler Town and Country Vibrating sound/feeling arou

Just got my van back from the shop. I took it in for vibrating and a strange clunking sound at 35-45mph and then again around 60mph. They replaced the struts in front, 2 new tires, tightened the tie rod on the drivers side and did an alignment. It seems to have fixed the clunking noise but 10 min. After picking it up (the shop closed after I walked out the door, of course) the vibrating happened 2 times at 40 mph. It does not happen all the time, my husband had to drive it for 10 min. To get it to do it. I am unsure what this could be and thought my $940 repair job would have fixed the problem. Help me please. I want me and my 3 little girls to be safe in the van. Thank you. Rhonda