worth a service call or time for more cost effective to replace?

Recently, dryer not starting sometimes. Sometimes hit start and hear motor hum but does not turn. I have taken apart and cleaned out lint. Noticed belt appears unaffected. Sometimes dryer starts fine but stops short time into cycle. I smell something hot inside like burning wires or motor but see no smoke or flames. I am not sure how old this unit is but have not seen a Montgomery Ward store in many years. I wonder if this dryer has outlived its life expectancy or worth a call to a service tech?
Thanks
Bruce